Periodic Table Trends and Properties

The mentioned element should have 3 shells and 6 valence electrons in the outermost shell. It must gain two electrons to attain a stable electronic configuration of 8 electrons in the outermost shell. Such elements which tend to gain one or more electrons are non-metals, so the mentioned element must be a non-metal.

It is the number of elements present in the second period (Li to Ne).

The atoms showing tendency to gain one or more electrons is said to be non-metallic. On moving down a group, the atomic radii of atoms increase. This results in less effective attraction from nucleus side for the electrons in the outermost shell. So, down th<span style="font-family:" arial;="" font-size:="" small;="">e group, the tendency to lose electrons increases, while the tendency to gain electrons is reduced. Hence, the non-metallic character <b style="font-family:" arial;="" font-size:="" small;="">decreases<span style="font-family:" arial;="" font-size:="" small;=""> as we go down a group.

An atom is said to be non-metallic if it gains one or more electrons when supplied with energy.

 Moving from group 1 to group 7, i.e., along a period from left to right, there occurs an increase in nuclear charge as well as decrease in atomic size. Both these factors make the electrons tightly bound towards the nucleus, thus making it difficult for them to be lost. This increases the electron affinity.

The total number of electrons present in the outermost shell of an atom represents the group number of the element.

There is increase in atomic no. as well as nuclear charge of the atoms of the elements when we go from left to right in a period. But, no new shell is added, which means more number of protons attracts the electrons present at the same distance from them. So there is a decrease in radius or atomic size of the atoms.

Number of period is equal to the number of shells occupied by the electrons of an atom in its ground state. So, the elements having same no. of electronic shells when their electronic configuration is represented in their respective ground states are placed in the same period.

 Atomic radii and nuclear charge increases on moving down a group. But, the increase in atomic radii dominates over the increase in nuclear charge, thus decreasing the ionization potential or ionization energy down a group.

Periods 2 and 3 are called short periods, according to the no. of elements contained in them (8).

Metallicity is the property of an atom of an element to lose one or more electrons when energy is supplied to it.

As we move from left to right, decrease in atomic size and increase in nuclear charge of an atom occurs. So, the electrons present in the same number of shells (same period) are pulled more effectively towards the nucleus, and hence increase in electro negativity.

Atoms having same atomic number (i.e. same number of protons but different number of neutrons in their nucleus) but different atomic mass (i.e. sum total of number of protons and neutrons) are known as isotopes.

Fluorine (atomic no. 9) has only two shells in its atomic state with 7 electrons in its outermost shell. So, it it tends to gain one electron to become stable. The 7 protons present in the nucleus and small size of the atom make it possibly the most electronegative element of the periodic table.

<span style="font-family:" arial;="" font-size:="" small;="">Li<span style="font-family:" arial;="" font-size:="" small;=""> occurs at the top of the alkali metals group. Number of shells increases down a group<span style="font-family:" arial;="" font-size:="" small;="">. So, Li is smallest with least no. of shells, with Na and K following the order.

On moving from left to right, the atomic size decreases due to increase in effective nuclear charge. From amongst the given elements, these occur in period 2 of periodic table in the order- beryllium, boron, nitrogen and fluorine (atomic numbers 4, 5, 7 and 9 respectively). Thus, atomic size decreases from beryllium to fluorine. Hence, beryllium has largest atomic size amongst the given elements.

Ionization energy is the energy required to remove electron from an atom in its ground state. The noble gases having completely filled outermost shell have no tendency to lose any electron. So, they have highest ionisation energy.

The atoms with atomic numbers 8(2, 6) and 16 (2, 8, 6) have six electrons in their respective outermost shells. So, they belong to the same group, i.e., 6^th group.

<span style="font-family:" arial;="" font-size:="" small;="">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.<span style="font-family:" arial;="" font-size:="" small;=""> <span style="font-family:" arial;="" font-size:="" small;="">So, non-metallic character increases<span style="font-family:" arial;="" font-size:="" small;=""> 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.

Electron affinity refers to the amount of energy released when an atom in its gaseous state accepts an electron to form an anion.

Occurrence of different elements with same atomic mass does not form any basis for these to be assigned some particular position in the periodic table. So, it is not a periodic property. This was a major drawback of the periodic table given by Mendeleev, who classified the elements according to their atomic mass. Also, it was observed by Moseley that the physical and chemical properties of elements depend upon the number of electrons in their outermost shell in ground state and not on their atomic masses.

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.

The size of P atom is larger than N because when we go from period 2 to period 3 a new shell is added which means there occurs an increase in atomic size (when we move down a group).