*Atoms, Ions and Compounds

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Atomic Structure and Isotopes

PROTONS = charge of +1, mass of 1

NEUTRONS = charge of 0, mass of 1

ELECTRONS = charge of -1, mass of 1/1836 (0)

Periodic table is arranged in order of ATOMIC NUMBER (number of protons)

Mass number = neutrons + protons

ISOTOPES = atoms of the same element, with different numbers of neutrons, so different mass numbers.

Isotopes of the same element REACT IN THE SAME WAY, only differing by physical properties (chemical properties, so reactivity, depends on (valence) electrons).

IONS = charged particle - an atom that has gained/lost an electron, making it charged

ANION = -vely charged

CATION = +vely charged

Relative Mass

RELATIVE ATOMIC MASS = the weighted mean mass of one atom of an element, compared with 1/12th of the mass of an atom of carbon-12. (Ar)

RELATIVE ISOTOPIC MASS = the average mass of one isotope of an element, compared with 1/12th of the mass of an atom of carbon-12. (Ir)

Mass spectrometry = measures the percentage abundances of each isotope present in an element (what proportion of each isotope is in the element). The ions are detected on a MASS SPECTRUM, as a mass-to-charge-ration (m/z = relative mass/relative charge), each ion reaching the mass spectrum detector adds to the SIGNAL. The greater the abundance, the LARGER the signal.

Ar and Ir = NO UNITS (ratios)

RELATIVE ATOMIC MASS = (% x mass) + (% x mass)/ total abundances (%'s)

You can't find the relative atomic mass of an isotope by adding the relative masses of subatomic particles as strong nuclear forces holding the protons and neutrons together leads to a slight MASS DEFECT (explains the need for the standard isotope of carbon-12)

Relative molecular mass/relative formula mass (Mr) = the sum of the relative masses of all the elements present in a compound, in the proportions that they are present in.

Mass spectrometry can be used to find out:

The relative abundances of each isotope present in an element (from which relative atomic mass can be calculated)

To identify unknown elements

Working out relative isotopic masses

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Formulae + equations

Polyatomic ions = ions containing multiple elements bonded together

Binary compounds = compounds containing two elements only

Compounds = multiple elements bonded together

Metals LOSE electrons, forming CATIONS. Non metals GAIN electrons, forming ANIONS

IONIC COMPOUND = contains a cation and an anion, and the charges cancel each other out