Question

. For each element below, state (i) the number of valence electrons in the atom, (ii) the electron dot structure, and (iii) the chemical symbol(s) for the most stable ion.
a. Ba


b. I


c. K

Answer 1

(i) You can work out the number of valance electrons an element has by looking at its group number. Whatever group its in, is how many electrons it has 'spare' to use for bonding with other elements. So basically, group number = no. of valance electrons, can you answer this using the information I've provided?

(ii) For this, you just have to draw shells with the no. of electrons it has on the shells. I'm not 100% sure if you need to draw the whole thing, or the electrons on the outer shell, however you can find out both of these things on the periodic table.

To find out the no. of electrons an element has, look at its atomic number on the element on the periodic table. Because your elements have no charge, the atomic number will be the same as the no. of electrons the element has.

To find out how many electrons are on its outer shell (valance electrons) look at its group number. That is how many electrons are on its outer shell.

I'll show you two examples of how you can draw the electron dot structure in the pictures provided. Then you can base the other two elements off of the one you choose (drawing out all the electrons or just the ones on the outer shell).

(iii) You can find out an elements ion by looking also, at its group number. Its group number will equal to its ion charge (most of the time). Elements in group 1, are on the left side of the periodic table.

Elements on the left side want to LOSE electrons to get a noble gas structure (8 electrons on its outer shell) to be stable (its easier to lose 1,2 or 3 electrons than try and gain 7, 6 or 5). This means its ion charge will be positive, because less negative (electrons) charge in the atom, the more positive the element becomes. Now, group 1 elements will have a charge of 1+ or just + as it has ONE positive charge because its in group 1. Group 2 elements will have a charge of 2+ and group 3 elements will have a charge of 3+.

Elements in group 4 are harder to tell its charge as it is exactly half way between group 1 and group 0/18/8, but luckily none of your elements are in that group, so it should be easy for you.

Elements on the right side of the periodic table will have negative charges as ions, because they also want to make a noble gas structure, however it is easier to GAIN 1,2 or 3 electrons, than lose 7,6 or 5. More of a negative charge (more electrons added/gained) will equal more of a negative than positive charge in the atom, making have a negative charge. So, you basically have to take the group number away from 8 to get how many electrons it needs to gain, and that will be its charge number. For example, elements in group 7 will have a charge of 1- or - as they need one more electron (or - charge) to have a noble gas structure. Elements in group 6 will have a charge of 2-, and elements in group 5 will have a charge of 3-.

So, for Ba, you would write Ba2+, as it is in group 2 on the left side of the periodic table.

Hopefully from this information you can answer your questions, and understand how to answer these types of questions for the future now. Good luck :)