Formula and equations - 2.3 - (3)
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In equations, how are elements shown simply as?
their symbol except from the few elements that exist as small molecules
What are diatomic molecules?
they are small molecules which contain two atoms bonded together
What are the 7 examples of diatomic molecules?
Hv2, Nv2, Ov2, Fv2, Clv2, Brv2, and Iv2
What other small molecules are there?
phosphorus and sulfur
What do covalent compounds not contain?
ions
How do most covalent compounds exist?
as molecules with a small number of atoms bounded together
What is an example of covalent compounds?
COv2 and Hv2O
In equations, what is used?
the formula of the molecule is used
In ionic compounds, what is used in equations?
the formula worked out from the ionic charges
What is the formula worked out from the ionic charges in ionic compounds called?
the formula unit
Why are state symbols shown in brackets after a formula?
to indicate the physical state
What are the four state symbols?
(g) - gas, (l) - liquid, (s) - solid, and (aq) - dissolved in water
To balance an equation, what do you need to do?
multiply each formula by a balancing number until the number of atoms of each element are the same on each side of the equation
Balancing numbers are written in…
front of each formula
When balancing an equation, what must you not change?
any chemical formula
Where should balancing numbers go in front of?
the chemical formulae and they are not subscripted
When is the equation balanced?
when there are the same number of atoms of each element on each side of the equation