I'm super stuck, and I have to turn in this huge packet tomorrow, can someone help me?

Question

anonymous · Answer

The first one I'm stuck on is:
Describe the trends in atomic size of elements within groups and across periods in the periodic table, and provide examples.

Like what? I'm totally blanking here.

matt101 · Answer

Atomic size decreases across a period but increases down groups. Let me explain:

PERIODS: As you move across a period, the number of protons in your atom increases, meaning there is a greater effective charge being exerted on its electrons. As a result, the atom is able to hold its electrons closer to the nucleus because there is a greater attraction.

GROUPS: As you move down groups, you're adding valence shells. This makes the atom physically larger.

I'll leave it to you to come up with examples, but you can take really any two elements in a period or in a group and compare them.

anonymous · Answer

So like.. Be would be smaller than both Mg and Li, because it's one after Li, and one above Mg?

anonymous · Answer

*Be* meaning Beryllium.

anonymous · Answer

@matt101 ?

matt101 · Answer

Exactly right! You just need to understand that reason it's smaller is different in each case (one due to attraction and the other due to valence shells).

anonymous · Answer

Thanks. :)