Questions:

1. A) Define atomic radius.

Ans: The atomic radius of an element is its mean or typical distance from its nucleus to the boundary of the surrounding cloud of electrons.

1. B) State and explain the trends in atomic radius for a period and a group.

Ans: The trend for atomic radius for a period, in this case period 2, the radius decreases, because the number of orbitals is steady, but the increasing number of protons pulling on the same number of increasing electrons makes a ‘tighter’ attraction.

The trend for atomic radius in a group, in this case group 1, is that the radius increases, as one step down the group adds a whole orbital.

2. A) Define density.

Ans: Density is the ratio between mass and volume.

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

Ans: The trend in density for period 2 and period 3 is that the densities increase till group 3, drop at group 5, increases till group 7, and the densities decrease at group 8.

3. A) Define electronegativity and electron affinity.

Ans: Electronegativity is the tendency of an atom to attract electrons in the formation of an ionic bond. Electron affinity is the amount of energy that is released when an electron is gained whether it is heat or light.

3. B) State the trends in electronegativity for periods and groups.

Ans: Electronegativity increases from left to right in a period, since the nuclear charge increases due to an increase in atomic number, except in noble gases, which are stable elements and have no need to attract other electrons.

3. C) Explain the trends in electron affinities for periods and groups.

Ans: Electron affinities increases for periods if you move left to right because the number of protons in the nucleus increases which causes a