Periodic Classification and Elements

Non-metallic character refers to the tendency of an atom to gain one or more electrons. On the left side of the periodic table, the elements having 1, 2 or 3 electrons in their outermost shell tend to lose them, thus exhibiting metallic character. On the right of it, the elements have 5, 6, or 7 electrons in their outermost shell, having a tendency to gain one or more electrons to be most stable, which is being non-metal. So, non-metallic character increases from left to right in a period.

Element with atomic number 13 has electronic configuration 2, 8, 3. It tends to lose the 3 electrons present in its outermost shell. The sulphate ion carries two negative charges over it. So, three ions of E must combine with two ions of sulphate ion to make a neutral compound. So, the compound must have a formula E₂(SO₄)_3.

The halogen in period 3 will be having 7 electrons in the outermost third shell. This must require one electron for its octet to be completed. So, each of its atoms needs to make bond with one hydrogen atom which donates its one electron and hence, the formula HX.

Phosphorus is a non-metal located in the p-block of the periodic table. Tin, lead, and radium are all metallic elements.

Tritium is a radioactive isotope of hydrogen, containing one proton and two neutrons in its nucleus.

Hydrogen is the first element in the periodic table and has the lowest atomic mass, making its atom the lightest.

The chemical symbol for Sodium is Na, derived from the Latin word Natrium.

The atomic number of an element is defined by the number of protons in the nucleus of its atoms. This number uniquely identifies the element.

Fluorine is a highly reactive halogen, which is a type of non-metal located in Group 17 of the periodic table.

Yttrium is a chemical element with the atomic number 39, and its chemical symbol is Y.

Hydrogen is the lightest element and makes up most of the universe (about 90% of the universe is made of hydrogen).

Boron is a non metal belonging to the p block. Being a non metal it is a poor conductor of electricity at room temperature but a good conductor at high temperature. The element is not found free in nature, but occurs as orthoboric acid which is usually found in certain volcanic spring water and as borates in boron and colemantie.

The elements of  Group 7  are known as halogens. The term halogen means salt-former and compounds containing halogens are called salts. The halogens exist, at room temperature, in all three states of matter - Gases such as Fluorine & Chlorine, Solids such as Iodine and Astatine and Liquid as in Bromine. The Halogen elements on the Periodic Table are: Fluorine, Chlorine, Bromine, Iodine, Astatine.

The existence of elements in two or more different forms is called allotropy & nthe different forms are called allotropes. In the case of oxygen, there are two forms: 'normal' dioxygen (O₂) and ozone, or trioxygen (O₃). These two allotropes have different molecular configurations. More commonly, allotropy occurs because of different crystal structures in the solid, and is particularly prevalent in groups 14, 15, and 16 of the periodic table. In some cases, the allotropes are stable over a temperature range, with a definite transition point at which one changes into the other. For instance, tin has two allotropes: white (metallic) tin stable above 13.2°C and grey (nonmetallic) tin stable below 13.2°C. This form of allotropy is called enantiotropy.Carbon also has two allotropes - diamond and graphite - although graphite is the stable form at all temperatures. This form of allotropy, in which there is no transition temperature at which the two are in equilibrium, is called monotropy.