Answer:
see explanation
Explanation:
Using the periodic table, look at the top of each column => These are group numbers ... Typically (for american tables) the numbers are divided into A-Groups and B-Groups... For this post, you need to focus on the A-Groups, or 'Main Group Elements'... Now, the numbers also represent the number of valence (outer shell) electrons in the elements listed below that number. For example, under Group IA, all elements ( H, Li, Na, K, Rb, Cs & F) all have one (1) outer shell electron. All elements under IIA have two outer shell electrons, IIIA, 3 outer shell electrons and so on. The exception is Helium (He) which has only 2 outer shell electrons and is typically listed under Group VIIIA.
So ...
X· => H, Li & Na
X: => He(noble gas exception), Be & Mg
·X: => B & Al
:X: => C & Si
X(5 dots) => N
X(6 dots) => O
X(7 dots) => F & I
X(8 dots) => Ne
