The Atom Flashcards
What is Dalton’s model of the atom?
John Dalton proposed that all matter is composed of very small things which he called atoms.
What is Thomson’s model of the atom?
After the electron was discovered by J.J. Thomson in 1897, people realised that atoms were made up of even smaller particles than they had previously thought.
What is Rutherford’s model of the atom?
Rutherford carried out some experiments which led to a change in ideas around the atom. His new model described the atom as a tiny, dense, positively charged core called a nucleus surrounded by lighter, negatively charged electrons.
What is Bohr’s model of the atom?
There were, however, some problems with Rutherford’s model: for example it could not explain the very interesting observation that atoms only emit light at certain wavelengths or frequencies. Niels Bohr solved this problem by proposing that the electrons could only orbit the nucleus in certain special orbits at different energy levels around the nucleus.
Define Relative atomic mass
The relative atomic mass of an element is the average mass of all the naturally occurring isotopes of that element. The units for relative atomic mass are atomic mass units.
Blurt all about the electron
The electron is a very tiny particle. It has a mass of 9,11×10−31
kg
. The electron carries one unit of negative electric charge (i.e. −1,6×10−19C).
Blurt about the nucleus
Unlike the electron, the nucleus can be broken up into smaller building blocks called protons and neutrons. Together, the protons and neutrons are called nucleons. The neutron is electrically neutral i.e. it carries no charge at all. Like the proton, it is much heavier than the electron and its mass is 1,6749×10−27kg (slightly heavier than the proton).
Blurt about the proton
The electron carries one unit of negative electric charge (i.e. −1,6×10−19
C
, C is Coulombs).
Each proton carries one unit of positive electric charge (i.e. +1,6×10−19C). Since we know that atoms are electrically neutral, i.e. do not carry any extra charge, then the number of protons in an atom has to be the same as the number of electrons to balance out the positive and negative charge to zero. The total positive charge of a nucleus is equal to the number of protons in the nucleus. The proton is much heavier than the electron (10 000 times heavier!) and has a mass of 1,6726×10−27 kg. When we talk about the atomic mass of an atom, we are mostly referring to the combined mass of the protons and neutrons, i.e. the nucleons.
Define the Atomic number (Z)
The number of protons in an atom.
Define the Atomic mass number (A)
The number of protons and neutrons in the nucleus of an atom.
Define Isotopes?
Isotopes of an element have the same number of protons (same Z), but a different number of neutrons (different N).
Define Atomic orbital
An atomic orbital is the region in which an electron may be found around a single atom.
Define Electron configuration
Electron configuration is the arrangement of electrons in an atom, molecule or other physical structure.
Define Valence electrons
The electrons in the outermost energy level of an atom.
Define Core electrons
All the electrons in an atom, excluding the valence electrons.
