Metals lose electrons in bonding whilst non-metals gain electrons during ionic bonding hence metals form cations and non-metals form anions. It is difficult for a non metal such as oxygen to lose 6 electrons to form a cation since it would need a lot of energy. When it comes to metals it is also difficult to gain that much elecrons since as electrons are added the effective nuclear charge increases each time.

Diamond is the hardest non-metallic element which is an exception. Sulphur is a non metal and is relatively brittle while others are metals and are hard, but not brittle.

Metals are hard and can be casted into thin sheets and wired example Al, iron etc. Therefore they are malleable and ductile respectively.
The valence electrons in metals are delocalized over several atoms that makes them good conductors. Metals react with oxygen to form oxides as:
$Ca+O _2 \rightarrow CaO$
these oxides reacts with water to yield metal hydroxide as:
$CaO+H _2O \rightarrow Ca(OH) _2$
Metal hydroxides are strong bases as they form hydroxide ions and the ion of the particular metal that it is made up of in aqueous phase. Example: When $Ca(OH) _2$ is dissolved in water, it forms two $OH^-$ ions and $Ca^{ 2+ }$ ions. therefore metal oxides are basic.
option A,B, ,D are correct

• As compared to metals, they have low density and will melt at low temperatures. The shape of a nonmetal cannot be changed easily as they tend to be brittle and will break. 
  
• Elements that have properties of both metals and nonmetals are called metalloids. They can be shiny or dull and their shape is easily changed.
  
• Hence High density is not associated with non-metals and so option A is correct answer.

Solution:- (A) Conduct electricity when molten

Malleability: Metals have the ability to withstand hammering and can be made into thin sheets known as foils. while non metals are generally brittle.

Gallium melts at room temperature and has one of the largest liquid ranges of any metal. The melting point of gallium is used as a temperature reference point. At room temperature, gallium metal is unreactive towards air and water due to formation of a passive protective oxide layer. It melts at $29.76^{\circ} C$ (slightly above the room temperature). It is used as an agent to make alloys and is also useful in semicounductors.

Sodium, potassium, lithium are soft metals and can be easily cut. It is the secong least dense metal after lithium. It is a soft solid that has a low melting point and can be cut with knife while iron and gold are hard and dense metals which are melleable and ductile.

Copper and steel are metals and metals are a good conductor of electricity generally. impure water contains ions which conduct electricity.  

Eraser, plastic ruler and safety pins are non-metals so they are not magnetic as per the characteristics of non-metals. but safety pins are metals and are magnetic in nature.

Door locks are usually needed to be strong to stop thieves or other trespassing. 

Metal which give out a musical note when struck are called sonorous.

Sonority (of a material) is the property of producing a ringing sound when struck. Most metals are sonorous. Therefore, they are used in many instruments (eg. cymbals and bells). Almost all non-metals are non-sonorous, i.e. they don't produce a ringing sound when struck.

Metals are a common type of ductile material. Copper, aluminum, and steel are examples of ductile metals. The opposite of ductility is brittleness, where a material breaks when tensile stress is applied to lengthen it. Examples of brittle materials include cast iron, concrete, and some glass products. Zinc is relatively more brittle than others.

Sodium is the soft silvery metal at standard temperature and pressure. It can be readily cut with a knife as it is very soft. When freshly cut sodium has a bright silvery luster. If exposed to air the surface rapidly tarnishes, darkening at first and then forming a white coat of sodium hydroxide and sodium carbonate.

Lead (II)acetate also known as sugar of lead,salt of saturn and Goulard's powder is a white crystalline chemical compound with a sweetish taste. It is made by treating lead ($II$) oxide with acetic acid.

The brilliant shine over the freshly cut surface of a metal is called lusture.

Metals are usually solid in nature. There is less metal that is soft in nature. Some metals are used to make items like coins because they are hard and will not wear away quickly. 

Lustre is the way light interacts with the surface of a crystal, rock, or mineral. There are various types of lustre like greasy lustre, metallic lustre, dull lustre etc.

Sonorous metals mean a deep, full, pleasing and imposing sound. It is one of the physical properties of a metal through which a sound is produced when metal is hit.

Non-metals are not malleable. They are brittle and hence they break easily. Such non-metals cannot be deformed by a hammer or rolling. Hence, non-metals cannot be deformed to form thin sheets.

All the metals are hard in nature. However, both sodium and potassium metals are soft and can be cut using a knife. The bonding in these metals is weak and electrons are not located over a single atom but over a number of atoms.

Sulphur, chlorine and xenon, all are $p-$block elements.

Most metals are hard except sodium and potassium. They can be easily cut with a knife. Osmium is hard enough to scratch glass.

Non-metals are not malleable. They are brittle and hence they break easily. Such non-metals cannot be deformed by a hammer or rolling. Hence, non-metals cannot be deformed to form thin sheets.

Graphite is a non-metal consisting of 3 carbon atoms. he weak attractions between the layers of atoms in graphite are easily broken. Therefore, graphite is soft and the layers can slide over each other.

Sodium and potassium are soft metal which can be easily cut with a knife.

Melting point of metals will be higher than non-metal. So, iron will have higher melting point.

Most of the metals are hard. But all the metals are not equally hard. The hardness varies from metal to metal. Most of the metals like iron, copper etc. are very hard. Sodium, potassium are exceptions.

Sound making property is known as sonority, i.e., when hit with an object they make sound.

Gold, silver copper have shiny surfaces, as they are metals. So are lustrous.

For a pure chemical, the mass concentration is equal to its density (mass divided by volume); thus the mass concentration of a component in a mixture can be called density of a component in a mixture.

Lustre is a property of metals i.e. they have a shiny surface.

Metals lose their lustre when kept exposed to air for long time and gets a dull appearance. It loses most of its shine and lustre.

Iodine has lustrous appearance. Bromine is a non-metal so is non-lustrous. Silver and iron are metals and they are lustrous.

Density, of a substance is define as mass per unit volume. Density $(\delta)$ is equal to mass $(m)$ divided by volume $(V)$. 

Zinc is used to galvanize metals, making them resistant to oxidation (rusting). Zinc is stronger reducing agent than the metal to be galvanized (such as iron) and hence, zinc can be more easily oxidised. Thus, during corrosion, zinc is oxidised. This prevents corrosion (rusting) of other metal.

When combined with trace amounts of chromium, beryllium takes on a beautiful green hue as the gemstone commonly known as the emerald.

Aluminium foils are impermeable to oxygen and water; thus are used for wrapping chocolates and foodstuff. 

Metals like lithium, sodium and potassium can be cut with a knife because their melting point is low as compared to other alkali metals. 

Sonority is the property of a metal in producing a characteristic resonant sound when struck. All metals are highly sonorous and sonority varies with metals.

Metals, in general, are hard as solids at room temperature but sodium is a metal that is exceptional. 

Metal 'M' is copper which is one of the best conductor of heat and electricity used in making electric wires is found in nature as sulphide ore $(Cu _2S).$

Alkali and alkaline earth metals have valence electrons as 1 and 2 respectively. In general, elements with 1-3 valence electrons can be metal except for hydrogen and helium (nonmetal) and Boron (metalloid). Also, transition elements have 2 valence electrons but since they can utilize d-orbital for bonding, therefore can have variable oxidation states.
Therefore in general  1-3 valence electrons can be meta.
Hence, option $A$ is correct.

Element that is relatively strong have strong force of attraction and difficult to break and are considered to be relatively hard.

The metallic lustre of a metal is due to the oscillation of loosely bound electrons.

Solubility in water depends on the size. Smaller is the size of the anion, more it is solvated and more is the solubility.

More the charge on the ions, more is the covalent character. Hence, the order of covalent charcter is $AlN  > MgO > NaF$. More is the covalent character, less is the solubility in water.

Elasticity is the property of solid materials to return to their original shape and size after the forces deforming them have been removed.

We have, $1\ cm^3 = 10^{-6}\ m^3$

Under standard conditions, lithium is the lightest metal and the least dense solid element. It is a soft, silver-white metal belonging to the alkali metal group of chemical elements.

Very few metals exist in the free or native state. Only metals like gold, platinum and mercury are occasionally found in the free state i.e in the pure form.

Metals have low ionization enthalpy value and as a result of which they have a high tendency to donate the electrons and achieve inert configuration,

The given statement is false as mercury,gallium and caesium are liquids at room temperature. 

Alkali metals are silver colored and their lustre tarnishes in air due to oxidation. Sodium has a distinctive flame colors because their outer $'s'$ electron is very easily excited.

Phosphorus is a very reactive metal, when exposed to air it starts reacting vigorously, therefore it is kept in water.

Mercury, bromine, gallium all exist in liquid state but bromine is non-metal.

All metals are solid state at room temperature except mercury.Hence,it is incorrect.

Iron is tougher than sodium because all metals have metallic bonding which is different from ionic or covalent bonding.In metallic bonding, the outer shells of adjacent atoms overlap and outer electrons are free to move through the lattice. Metal cations are balanced by electron anions.

The metallic lustre is because the excited $3s$ electrons of sodium emit a photon when they fall from $3p$ to $3s$ and the oscillation of electrons causes the metallic lustre.

Lead($II,IV$) oxide also called minium, red lead or triplumbic tetroxide is a bright red or orange crystalline or amorphous pigment. It is used in the manufacture of batteries,lead glass and rust proof primer paints.

The correct sequence can be written as; c b d a.

Wooden scale, glass test tube, paper basket are all non-metals and a poor conductor of electricity and Rubber gloves are similar to these.

Tensile strength is a measurement of the force  required to pull something such as rope, wire or a structural beam to the point where it breaks.

The tensile strength of a material is the maximum amount of tensile stress that it can take before failure, for example breaking.

Density is a ratio of mass and volume.

Mercury is the only metal that is liquid at room temperature. Its elasticity property is remarkably low. Hence, when struck it does not produce sound.

A metal is a lattice of metal "ions" in a "sea" of delocalised electrons - mobile electrons. Photons of light do not penetrate very far into the surface of a metal and are typically reflected, or bounced off, the metallic surface, by the mobile electrons and what you get is metallic reflection, which is lustrous.

Silver has a very considerable elasticity. When struck it produces a very acute sound. Hence, it the most sonorous metal.

$A,\ B$ and $C$ are all metals with free electrons. Photons of light do not penetrate very far into the surface of a metal and are typically reflected or bounced off the metallic surface by the mobile electrons and what you get is a metallic reflection, which is lustrous.

Metals (except sodium, potassium) have very high tensile strength.
For example - iron can bear a lot of tensile strength. So, it is used in construction of buildings, bridges, railway lines etc.

Phosphorus is a non-metal. It do not have free electrons for conduction. So, it is bad conductor of electricity.

Now, 1 $mm $ =   0.1 $cm$

Mass of piece of paper $=0.02\;g$

Mass  of the sphere, $M = Density \times Volume$

Hydrogen

Metals have a high density hence they feel heavy for their size whereas non-metals have a low density.

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is $\rho$.

Metals are generally malleable — that is, they can be hammered or pressed permanently out of shape without breaking or cracking — as well as fusible (able to be fused or melted) and ductile (able to be drawn out into a thin wire). 

The high density of most metals is due to the tightly packed crystal lattice of the metallic structure.

 The alkali and alkaline earth metals in groups $I :A$ and $II :A$ are referred to as the light metals because they have low density, low hardness, and low melting points.

Sonorous, i.e., making a sound when it is a property of the metal. Iron being a metal is sonorous whereas hydrogen and sulphur are non-metals.

Galvanisation is the process of applying a protective zinc coating to iron or steel, to prevent rusting. The most common method is hot dip galvanizing, in which steel sections are submerged in a bath of molten zinc. Hence, zinc plating is the most durable metal plating on iron to protect against corrosion.

Ans : A Krypton molar mass $83.3\ g/ mol$, atomic radius III picometers.

The densest chemical element is osmium(which is a metal). Osmium has a density of around 22 grams per cubic centimeter, about twice the density of lead.

It should be light to make aerospace material. Beryllium has low density and also has high thermal conductivity.

Gallium is a metal with lowest melting point. When we hold it and apply pressure with fingers, It melts at room temperature because of low melting point so, it is used by magicians.

The basic difference between metals and non-metals is the extent of bonding.Metals have very high extent of bonding than that in non-metals which makes the metal malleable.

Like non-metals, zinc is an exception among metals that does not shows malleability.

Malleability is the property of metal whereas non-metals are generally brittle,non conducting and have low density.

Malleability in metals occurs because of the metallic bonds that keep the atoms in place. Metallic bonds, characterized by a 'sea' of electrons that easily move from atom to another, allow the metal atoms to slide past each other if a force is applied. Non-metals are hard and brittle due to the absence of these electron pools of metallic bonds. 

Metals are malleable. In given options, carbon is non-metal and thus is hard and non-malleable. 

Oxidation of sodium gives sodium oxide, $Na _2O$ and about 20% sodium peroxide,$Na _2O _2$.

Carbon is a non-malleable element. Malleability is a physical property of matter, usually metals to bend or be hammered into other shapes without breaking. Carbon do not deform due to absence of the  metallic bonds which is required to be malleable as it keep the atoms in place and allows one electron slip over another. 

Potassium is an extremely active metal that reacts violently with oxygen in air. Potassium oxidizes faster than most metals and forms oxides with oxygen-oxygen bonds. Three species are formed during the reaction: potassium oxide, potassium peroxide, and potassium superoxide.

The highly reactive metal is $P$ as it reacts with cold water. This is because, the reaction with cold water requires lowest energy of activation.

1) ornaments and brass utensils both are made up of metals.

2) Metals are lustrous because of the free electrons they have.

3) The free electrons can move freely in the metal causing any light incident on them to get reflected back.

4) This reflection is specular reflection rather than diffused and thus the metal surface appears shiny or lustrous.

Ag metal would be displaced from the solution of its salt by Mg, Zn or Cu metals.

 Pig iron has a very high carbon content, typically 3.8–4.7%, along with silica and other constituents of dross, which makes it very brittle, and not useful directly as a material except for limited applications.

As moving down of bottom of diagram metals becomes more reactive oxides will be hard to reduce.A given metal can reduce the oxides of other metal which lies above it in Ellingham diagram.