chemistry sem 1

Atomic number

The number of protons in the nucleus of an atom

Mass number

The number of protons and neutrons in the nucleus of the atom

Relative Atomic Mass

the ratio of the av mass of the atom to 1/12 C-12

Uses of Mass Spectrometry

Used for the quantitative determination of chemical elements using the absorption of light by free atoms in the gas phase.

Emission Specta

When chemicals are heated, the electrons absorb energy and go into a higher energy shell or orbital. This is an unstable electron configuration and the electrons are said to be in an ‘excited’ state. These electrons will release energy in the form of light to achieve stability and the electrons will return to their original position known as ‘ground state’.

Use of Absorption Spectroscopy

Used to determine quantitatively the concentration of specific elements in a substance by using the absorption of light of free atoms in its gaseous state.

Absorption Spectroscopy

An unknown sample tested for known element. ex. lead 1.) Unknown sample is vapourised (converted to gaseous state) 2.) Passed through a lamp containing known element e.g. lead that if vapourised sample contains pb, then ‘excited’ pb atoms emits light from excited lead atoms of vapoursied sample that produce the right mix of wave lengths to be absorbed by any lead atoms in the sample. AAS- a beam of electromagnetic radiation is emitted from the excited lead atoms and is passed through vapourised sample. The greater the number of lead atoms that are present in the sample, the more radiated light absorbed. 3.) A calibration curve is made measuring by several samples of known lead concentration under same conditions as the sample being tested. Calibration curve are compared to the amount of unknown sample absorbs.

Atoms

When the number of protons and electrons are equal. Atoms are held together by electrostatic forces of attraction between the neutrons and electrons

Isotopes compared to Elements

Isotopes posses the same electron configuration and similar chemical properties but have different physical properties due to difference in number of neutrons.

MS purpose

To determine the isotopic composition of elements and interpret to determine relative atomic mass

Exceptions for covalent compound systematic naming

oxalate, peroxide, hydrogen peroxide

Physical properties of isotopes

hardness, density, lustrous, melting/boiling point, malleabililty/ductile/brittle