C1

C1

1. Identifying Element in compounds using symbols!

   • C stands for carbon, O stands for oxygen, S stands for sulfur and Na stands for sodium.
     • the formula for carbon monoxide is CO
   • when writing your symbols and formulae. Be careful about when to use capital letters. For example, CO means a molecule of carbon monoxide but Co is the symbol for cobalt (an element).

2. Notice that the three hydrogen atoms have the same number of protons, but a different number of neutrons. These atoms are called isotopes, which are atoms of the same element that have a different number of neutrons. Review: Neutrons are all identical to each other, just as protons are.

3. Atoms with different neutron numbers

4. Atomic Structure

   • Every atom is made of a nucleus consisting of protons and neutrons. The nucleus is surrounded by electrons. Protons and electrons are oppositely charged. Neutrons have no charge. This means the nucleus of an atom is always positively charged. An atom has a neutral overall charge because it has the same number of electrons as protons. Protons and neutrons have the same mass. Electrons have such a small mass that this can usually be taken as zero.

5. Symbol Formulae

   • Symbol equations. Each of the reactants and products is shown as a formula.The numbers in front of the formulae are there to balance the equation. This gives the same number of atoms of each element on each side of the equation