Leaving Cert Chemistry- The Periodic table

an element

cannot be split into a simpler substance by chemical means

a triad

A group of three elements with similar properties in which the atomic weight of the middle element is the average of the other two

Newland's Octaves

Arrangements of elements in which the first and the eighth element, counting from a particular element, have similar properties

Mendeleev's Periodic Law

When elements are arranged in order of increasing atomic weight the properties of the elements recur periodically

The atomic number

Number of protons in the nucleus of an atom

Modern Periodic Table

arrangement of elements in order of increasing atomic number

Modern Periodic Law

When elements are arranged in order of increasing atomic number, the properties of the elements recur periodically

The Mass number

sum of the number of protons and neutrons in the nucleus of an atom

Isotopes

Atoms of the same element that have different mass numbers due to different number of neutrons in the nucleus

Relative atomic mass (Ar)

Average of the mass numbers of the isotopes of the element, as they occur naturally, taking their abundance into account and expressed on a scale of Carbon-12

Principle of mass spectrometry

Charged particles moving in a magnetic field are deflected to different extents according to their masses and are thus separated according to these masses

electron configuration

the arrangement of electrons in an atom of an element