beginner in chem .. help please?

Question

i need help on how many molecules are in each.. not sure what's the difference between an ion and molecule ... :(

2O 2
H 2O
3H 2
4H 2O

Answer 1

(2)O 2 = 2 molecules of oxygen

(1)H 2O = 1 molecule of water

(3)H 2 = 3 molecules of hydrogen

(4)H 2O = 4 molecules of water

Answer 2

Compounds are made of molecules. They have no charge.

An ion is an atom (or group of atoms) with a charge (positive or negative)

In chemical "shorthand" if there is a number in front of a compound (called a coefficient) it indicates the number of molecules. If there is a number written to the right and slightly below the line of writing (called a subscript) it indicates how many atoms of that element are in the compound. In both cases the number "1" is understood and is not usually written (after all, if you didn't have at least 1 you wouldn't be wrting the thing down anyway!).

In your questions just look at the numbers to the left of the formulas (coefficients) and that will tell you how many molecules you have. Remember, if there is no number written it is an implied "1"

Answer 3

1) You have two O2
O2 O2

2) 2 Hydrogens and 1 Oxygen

3) You have three H2; 6 hydrogens total.
H2 H2 H2

4) you have four H2O (water); 8 hydrogen and 4 oxygen.
H2O H2O H2O H2O



An ion is usually a positive charge atom, such H+. Negative ions are called anions.

When two or more atoms are joined together, it's a molecule. Example is H2O, H2, O2, CL2,...

H by itself is not a molecule...it's an atom.
O by itself is not a molecule...it's an atom.

Answer 4

For the no. of molecules just see the coefficent written before the formula.Generaly 1 is not written to indicate 1 molecule.Molecules are electricaly neutral species.But ions have perticular charge (+ or -)

Answer 5

A molecule is a group of atoms held together by chemical bonds (ex. O2). Ions are molecules or atoms with a charge (ex. Na+).

Answer 6

2O2= 2
H2O= 1
3H2= 3
4H2O= 4,,,

the coefficient is the no. of molecules. ^_^