Problem+Set+9

1. Describe the trend in atomic radii as one moves a) down a group and b) across a period.

a) at the start of a new group, the atomic radii jumps up. b) when it moves across a period, it decreases. (Nick DiBartolo)

2. At the beginning of each new group, the number of electrons increases so that one electron now occupies the next principal energy level's S orbital. More orbitals take up more space, so the atomic radius is bigger. Across a period, the atomic radius decreases because the farthest electrons are all in the same energy level. But there are more neutrons and protons, and they are much bigger than electrons, so they pull the electrons in towards the nucleus, reducing the atomic radius. (Emily Westel)

3. a) At the start of a new group, the ionic radii goes uo b) when it moves around a period, it decreases ( basically the same as number 1) (Becky Lee)

4. A sodium ion is smaller than a sodium atom because when a sodium atom becomes an ion it loses and electron and the electron configuration goes from [Na] 1s2 2s2 2p6 3s1 to [Na] +1 1s2 2s2 2p6. A sodium ion loses the electron that occupies the 3s orbital so the ion becomes much smaller than the atom, which still has an electron in the 3s orbital. (Andrew V.)

5. The oxygen atom would have a larger ionic radius because although their electron configurations are identical, magnesium has more subatomic particles which means a larger nucleus so there is a stronger charge; therefore, the electrons are attracted closer to the nucleus creating a smaller radius. (Rachel. H.)

8. a) At the start of a new group, the electronegavity becomes smaller b) When it moves across a period, it increases. (Shane Nediyakalayil)