Introduction to periodic table

Question 1

what are isotopes?

Answer 1

isotopes differ in the number of neutrons in their atoms

Question 2

say 2 things about elements

Answer 2

1. elements ( atoms) are arranged in order of increasing atomic number
2. all elements in the same group have similar properties

Question 3

what does the term ‘group’ mean?

Answer 3

a group is all the elements in one column. they all share the same chemical properties because they all have the same valence electron structure

Question 4

what does the term ‘ period’ mean?

Answer 4

A period is a horizontal row in the periodic table. So far, there are 7 of them.

Question 5

how can the atomic number and the mass number determine the number of neutrons, protons and electrons?

Answer 5

protons = atomic number
electrons = atomic number
neutrons = rounded atomic mass - atomic number

Question 6

explain the classification of elements as metals or non-metals on the basis of their electrical conductivity and the acid-base character of their oxides

Answer 6

Metals are all conductors. Metals form metal-oxides which are alkaline.

Nonmetals don’t conduct. They form nonmetal-oxides which are acidic.

Question 7

why do elements in the same group of the periodic table have similar chemical properties?

Answer 7

Elements in the same group have the same number of electrons on their outer shell.
This means they will behave in a similar way; they will react and bond similarly.

For example in group one, the elements all form +1 ions as they each loose one electron to become stable (to have a full outer shell).

Question 8

deduce the electronic configurations of the first 20 elements from their positions in the Periodic Table

Answer 8

Groups are columns in the periodic table; the group number represents the number of electrons on the outer shell.

Periods are rows on the periodic table; the row corresponds with number of shell.

So if you have an element on the third row down in group seven: it will have three shell and 7 electrons on its outer shell.

Question 9

what is an ion?

Answer 9

• atoms can give, take or share electrons to get a full outer shell
• an ion is an atom that is charged because it has gained or lost an electron
  example: Sodium, Na 2, 8, 1
  11 protons= 11+
  11 electrons= 11-
  ion/ sodium, Na+ 2, 8
  11 protons= 11+
  10 electrons= 10-

Question 10

which are the noble gases?

Answer 10

• group 0
• full outer shell- atoms are very stable
• monatomic

Question 11

deduce the number of outer electrons in a main group element from its position in the Periodic Table.

Answer 11

The groups (that’s going down the periodic table) tell you how many electrons are on the outer shell!

Also note that the periods (going across) tell you the number of orbitals the atom has.