PS1-2 Review 9th Grade

What are electrons? How do we count them?

Electrons are negative parts of an atom. We count electrons by filling in 2 seats in the first row closest to the nucleus and every row after that has 8 seats. NOT ALL SEATS will be filled up.

What are Valence Electrons?

The VALENCE electrons are the electrons on the most outside shell.  You can either draw out the atom with all the layers OR you can look at the top number (such as 3A) and that will tell you how many valence electrons there are.

What is an ion? How do I know the charge change?

An ion is a atom that has lost or gained an electron (-).  Atoms can NEVER gain or lose a proton (+) and keep being the same thing.  Atoms become ions because they want a perfect outer shell (2 if in the middle and 8 on the outside.)

An atom starts with equal number of protons and electrons.  Since it can only lose electrons (-), it will only increase in POSITIVE charge IF it LOSES an electron.  However many it loses is however many positive charge it is.  If it GAINS electrons, the atom has a NEGATIVE charge for however many electrons (-) it gains.

What are the charge of these elements? ¹¹Na, ⁷N, ¹⁰Ne

Na¹+, N³-, Ne

Ionic Bonding. (you may see the answer)

Because of the POSITIVE and NEGATIVE CHARGES of IONS, the reactions bond (like magnets).

This is why the LEWIS DOTS METHOD helps.  It shows where electrons can be lose or where it can go.

Covalent Bonding: The “other” type of bonding is between NON METALS.  They share electrons. Remember, 2 or more metals.