[scienceflunk]

I need some help on a few things I can't seem to find in either my book, nor my notes. I'm doing a phsyical science review paper, including definitions, and questions which is due tomorrow, and I've missed a bit of school already. So, some things I need help with are:

1.)At what temperature water has its greatest density?

2.)What part of the atom dictates its chemical properties?

3.)Given the atomic mass and atomic number, how do I calculate the number of protons, electrons and neutrons are in that element?

4.)How an atomic spectrum is made.

5.)How many valence electrons are in the main group of elements of the periodic table?

6.)What 7 diatomic elements are?

7.)How to tell an ionic compound from a covalent compound?

8.)What can be changed and what cannot be changed when balancing a chemical equation?


--To be honest, I completely stink at science. I can't get the hang of it, so if anyone could help me out, it'd be GREAT! Please and thank you.

[Ragib]

1. 2.97 Celsius
2. The electrons, primarily the outer shell.
3. Atomic Number is the number of protons, atomic mass is protons+neutrons, so the difference is the number of neutrons. The number of protons are the same as the number of electrons.
4. Heating the atoms up and seeing what wavelengths are emitted.
5. Main Group? Thinking you mean Transition metals, it varies.
6. Diatomic Elements are elements that are found as molecules of 2. Most gases, ie Oxygen, Nitrogen etc, You find 7 gases...
7. Ionic Compounds are formed by exchanging electrons to achieve an overall neutral charge. Covalent Bonds are when the atoms share pairs of electrons, to give each other the illusion of a full outer shell. Covalent Bonds are usually stronger.
8. You can not change the total number of original atoms, total atoms of each element. You can change the number of each element in one of the compounds, as long as you balance it to satisfy what I said before.

Hope this helps, Good Luck.