Hai :3
Do you know how to find valence electrons? The amount of valence electrons that an element has depends on its group number, with an exception towards transitional elements.
For example, Oxygen is in group 16, which makes it have 6 valence electrons. Group 1 has 1, group 2 has 2, group 13 has 3, group 14 has 4, and so on.
What about transitional elements? The elements ranging from group 3 until 11 have different valence electrons because (advanced) if you look at their electron configuration, they have d orbital electrons (they can be edited), which gives them a varied valence configuration.
1. Iodine: Group 17 - 7 valence electrons Calcium: Group 2 - 2 valence electrons Chlorine: Group 17 - 7 valence electrons Sodium - Group 1 - 1 valence electron Neon - Group 18 - 8 valence electrons Copper - Group 11 - *Copper is a transitional element!* Those within group 11 usually have either 1 or 2 electrons. Your teacher did not specify which copper he's asking, so you could say that there is Copper (I), which has 1 valence electron, and also Copper (II), which has 2 valence electrons.
Moving to your second question, to see how many electron shells an element has, you look at where they are in their period (horizontal row)
For example, oxygen is in period 2, therefore, it has two electron shells. Period 1 has 1, period 2 has 2, period 3 has 3, and so on.
1. 1. Iodine: Period 5 - 5 electron shells Calcium: Period 4 - 4 electron shells Chlorine: Period 3 - 3 electron shells Sodium - Period 3- 1 electron shells Neon - Period 2 - 2 electron shells Copper - Period 4 - 4 electron shells
