The metals which are found in free state in nature are silver, gold and platinum.

Hydrogen is a non-metal with atomic number one.

Bronze is an alloy consisting primarily of copper and the addition of other metals (usually tin) and sometimes arsenic, phosphorus, aluminium, manganese and silicon.

Mendeleev stated the famous periodic law according to which, "Properties of elements are a periodic function of their atomic weights''. Mendeleev arranged elements in the increasing order of their atomic weights in the form of a table, which is known as Mendeleev's Periodic Table.

Group 18 elements are known as inert elements. For example, helium, neon, argon, krypton, etc.

A newly discovered element M is placed in group IA of the periodic table because it forms an ionic chloride having the formula MCl.

The limitation of Newland’s Law of Octaves: In order to fit elements into his table, Newlands adjusted two elements in the same slot, but also kept some unlike elements under the same slot. Cobalt and nickel are in the same slot and are placed in the same column as fluorine, chlorine and bromine which have very different properties. Thus, Newlands Law of Octaves worked well with lighter elements only.

Some elements, like the transition metals, have electronic configurations in which electrons from their inner shells can also be used as valence electrons; these elements can have several different oxidation states. Chromium can have a valency of +2, +3 or +6.

Element X₁₀ has complete octet as its electronic configuration is 2, 8.

From the given configurations, 2, 8, 8, 2 would be the configuration of a metal as it will show positive oxidation state by losing 2 valence electrons.

Xenon is the most electropositive among all the noble gases.

In modern periodic table, there are 18 columns and 7 periods.

Aluminium ion has the largest size than all the other given ions.

Fe, Co, Ni and Cu elements belong to the same period and thus, have nearly the same atomic radius.

The ionisation energy of sulphur is less than that of phosphorus because phosphorus has half-filled electronic configuration.

The size of anion is always greater than the corresponding atom. Thus, only statement 1 is correct.

The valency of an element having atomic number 18 (argon) will be zero because it is a noble gas.

Sodium and potassium both are alkali metals. Thus, they have the same valency.

The number of valence electrons is the number of electrons in the outer shell that the atom uses for bonding. Nitrogen has 5 electrons in its n = 2 (outer) shell.

John Newlands arranged the then known elements in the increasing order of masses. He started with the element having the least atomic mass (hydrogen) and ended at thorium, which was the 56^th element.