1. (a). Define Atomic radius?

Ans. The distance from the centre of the atom to the outermost electrons is called the Atomic radius.

(b) State and explain the trends in the atomic radius for the period and a group.

Ans.  As you move across a period the atomic radius decreases except for the noble gases, because there is a stronger force of attraction pulling the electrons closer to the nucleus resulting in a smaller atomic radius.

  1. (a) Define Density.

Ans. A degree of consistency measured by the quantity of mass per unit volume is called density.

(b) Compare the trends in density for period 2 and 3.

Ans.  The density first starts to increase and as we move further from left to right it decreases as the tale moves towards the noble gases which are less dense than solids.

  1. (a) Define electronegativity and electron affinity.

Ans. Electronegativity: Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.

Electron Affinity: the energy change that occurs when an electron is added to a neutral atom in the gaseous state.

(b) State the trends in electronegativity for periods and groups.

Ans. As you move from left to right across a period, the electronegativity increases due to the stronger attraction that the atoms obtain as the nuclear charge increases.

Moving down in a group, the electronegativity decreases due to the longer distance between the nucleus and the valence electron shell, decreasing the attraction.

(c) Explain the trends in electron affinities for periods and groups.

Ans. Electron affinity increases across a period decreases down a group.

  1. (a) Define Ionization energy.

Ans. The quantity of energy required to remove an electron from an atom or ion in gaseous state.

(b) State and explain the trends in ionization energies for groups and periods.

Ans.   As you move down a group, ionization energy decreases.  Because electrons are further from the nucleus and thus easier to remove the outermost one.  As you move across a period the ionization energy increases, because as you move across a period, the atomic radius decreases and the atoms are smaller.  The outer electrons are closer to the nucleus and more strongly attracted to the center.  Therefore, it becomes more difficult to remove the outermost electron.

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