Edexcel C2 Gcse Revision

a) 1

b) 1

c) 1/1836 (1 divided by 1836)

Dmitri Mendeleev in 1869 (you don't need to know the date). He put elements with similar properties underneath each other in the table, so that they were in the same group. Each group went in order of increasing atomic mass.

He realised that there was a pattern of the atomic structure of each atom in a group, and found that not all elements could be known as the pattern was sometimes broken. As a result, he left gaps in the table where he thought new elements could be put when they were discovered.

12 <---Mass number - protons + neutrons

C <---1 or 2 letters-the symbol of the element

6 <---Atomic number - number of protons

Remember: the mass number and atomic number may sometimes be in a different position - the atomic number may be above the symbol etc. Just remember, it is always the bigger number which is the mass number.

The number of protons is the smaller number. The number of electrons is equal to the number of protons, so is the same.

The number of neutrons is the atomic number minus the number of protons.

They surround the nucleus in several shells. Each shell can only hold a specific number, so the excess electrons go onto the next shell. The first shell can hold 2, the second and third can hold 8. You won't need to know the others.

It is how the number of electrons in each of an atom's shells can be shown. The electrons are written as numbers, shell by shell. For example, argon has 2 electrons in its first shell, 8 in its second, and 8 in its third. Therefore, its electronic configuration is 2.8.8

The number of shells the atom has is the same as what number period it is in.

The number of electrons in the outer shell is the same as what number group it is in.

The shells have less energy if they are closer to the nucleus. Electrons will always fill the lower energy shells first.

The idea that elements in the same group periodically show the same properties due to their similar electronic structure.

An electrostatic bond between positive and negative ions. Both ions in the bond will either give electrons to or receive them from, the other, in order to make a full outer shell and be more stable.

By the atom's electronic configuration. It shows us how many electrons are in its outer shell, so we can work out how many it needs to gain or lose to become stable.

E.g.

Oxygen = 2.6. It will gain 2 electrons to have a full outer shell, so will become a negative ion as it gains electrons.

Magnesium = 2.8.2. It will lose 2 electrons to have a full outer shell, so will become a positive ion as it loses electrons

The suffix of their element name is replaced by the suffix '-ide.'

E.g. Fluorine becomes fluoride

Its symbol and its charge.

An ion which is formed from atoms of only one element.

A positive ion formed from atoms of more than one elements.

1) Write the name - calcium nitrate

2) Write its ions - Ca 2+ NO3 -

3) Multiply the number of ions so that the number of negative charges is equal to the number of positives - 1 x Ca 2+ = 2 x +

- 2 x NO3 - = 2 x -

4) Write the formula - Ca(NO3)2