Formulae Flashcards
What is an element?
A substance made from atoms with the same number of protons (atomic number) in the nucleus.
What is an atom?
The smallest part of an element that still has it’s chemical properties.
What’s a molecule?
2 or more atoms chemically joined together. Most elements that are gases at room temperature exist as molecules with 2 atoms.
They are shown by chemical formulae, H[2[, N[2] etc.
What’s a compound?
2 or more different elements chemically joined together.
(The chemical formula for methane is CH[4]. Each methane molecule has:
1 carbon atom
4 hydrogen atoms
1 +4 = 5 atoms in total
atoms of 2 elements joined together
What is a chemical symbol?
Each element has it’s own chemical symbol.
- It consists of 1, 2, or 3 letters
- Starts with a capital letter
- Has any other letters in lowercase
Give the meaning of the term ion.
An ion is a charged particle formed when an atom, or group of atoms, loses or gains electrons.
(Metal atoms lose electrons to form positive ions
Non-metal atoms gain electrons to form negative ions)
In copper carbonate, there is one carbon atom and three oxygen atoms for every copper atom. State the formula for copper carbonate.
CuCO[3]
No marks if 3 is shown as superscript or element symbols do not start with capital letters
Write the formula for sodium sulfate.
Na[2]SO[4)]
(A sodium ion has a single positive charge and a sulfate ion has 2 negative charges. Two sodium ions balance the charge on one sulfate ion.)
The formula for bromine is Br[2]. Explain what this shows.
A molecule consists of 2 bromine atoms chemically joined together.
The formula for magnesium hydroxide is Mg(OH)[2]. Explain what this tells us about the number and type of each atom or ion present.
(Multiply the numbers inside the brackets by 2.)
Two from the following for 12 mark each:
- It contains 2 oxygen atoms and 2 hydrogen atoms for every magnesium atom.
- It has 3 different elements/five atoms in total, chemically joined together.
- It contains one magnesium ion and two hydroxide ions.
An ion is represented as Na[+]. Explain what this shows.
The ion has one positive charge and it is formed from a sodium atom.
(Write the charge as a superscript at the top right of the symbol.
You should show a single positive charge as + and a single negative one as -)
An ion is represented as SO[4,2-]. Explain what this shows.
The ion has 2 negative charges, and it is formed from one sulfur atom and four oxygen atoms chemically joined together.
(Write the charge as a superscript at the top right of the symbol.
You should show a single positive charge as + and a single negative one as -)
