Chapter 2 - Atomic Structure Flashcards
what is an element?
a substance that cannot be further divided into simpler substances by chemical methods; all the atoms of an element contain the same number of protons
what is a compound?
a substance formed by the chemical combination of two or more elements in fixed proportions
what is an electron?
a subatomic particle with negligible mass and relative charge of -1; present in all atoms and are located in the shells (energy levels) outside the nucleus
what is a proton?
a subatomic particle with a relative atomic mass of 1 and a charge of +1 found in the nucleus of an atom
what is a nucleus?
the central region of an atom that is made up of the protons and neutrons of the atom; electrons orbit around the nucleus in different shells or energy levels
what is a neutron?
an uncharged subatomic particle present in the nucleus of atoms, has a relative mass of 1
what are subatomic particles?
very small particles from which all atoms are made
what is the proton number (or atomic number) (Z)?
the number of protons in the nucleus of an atom
what is the mass number (or nucleon number) (A)?
the total number of protons and neutrons in the nucleus of an atom
what is the a mass spectrometer?
an instrument in which atoms or molecules are ionised and then accelerated; the ions are then separated according to their mass
what does relative atomic mass (Ar) refer to?
the average mass of naturally occurring atoms of an element on a scale where the carbon-12 atom has a mass of exactly 12 units
what are isotopes?
atoms of the same element that have the same proton number but different nucleon number; different number of neutrons in their nuclei
what does electron shells (energy levels) refer to?
the allowed energies of electrons in atoms - electrons fill the shells starting with the one closest to the nucleus
what is the atomic theory?
a model of the atom in which electrons can only occupy certain shells moving outwards from the nucleus of an atom
what is meant by electronic configuration?
a shorthand method of describing the arrangement of electrons within the electron shells of an atom; also referred to as electronic structure
