atomic structure

• Protons are positively charged particles that are contained in the nucleus of the atom (the centre) and have a mass of 1amu (atomic mass unit).
• Neutrons are particles with no charge that are also contained in the nucleus of the atom and have a mass of 1amu.
• The nucleus has an overall positive charge as it contains the protons.
• Every atom has no overall charge (neutral) because they contain equal numbers of positive protons and negative electrons.
• Each element has its own atomic number.
• Elements are arranged in the periodic table in order of increasing atomic number.
• The mass number is given at the top left of the element's symbol, for example, sodium has a mass number of 23.
• The atomic number of sodium is 11, indicating that it has 11 protons and because it is neutral it has 11 electrons.
• The mass number of an element tells us the number of protons AND neutrons in an atom (i.e. the two particles that have a measureable mass).
• Sodium has a mass number of 23amu, indicating that it has 11 protons and 12 neutrons in an atom.
• Isotopes are atoms with the same atomic number but different mass number.
• Elements are made up of isotopes, hence the mass given in the data booklet is called the relative atomic mass (RAM).
• The relative atomic mass of each element shown in the data book is calculated from the masses of all the isotopes of an element taking into account the percentage proportion of each.
• The electron arrangement of all atoms can be found in the data booklet.
• All the electrons are arranged into energy levels, with the first energy level (the one nearest the nucleus) being able to hold a maximum of 2 electrons and the others being able to hold up to a maximum of 8 electrons (only true for the first 20 elements).
• Elements in the same group of the periodic table have the same number of outer electrons, which is the number of outer electrons that give an element its chemical properties.
• An atom consists of a nucleus containing protons and neutrons, surrounded by electrons.
• The number of protons and neutrons found inside the nucleus of an atom is referred to as the mass number.
• A neutron has no charge and a mass of 1 relative to a proton.
• The central part of an atom is referred to as the nucleus.
• A proton has a positive charge and a relative mass of 1.
• The periodic table brings order to information about the chemical elements and helps chemists to understand why elements react as they do.
• There are more than 100 elements which are arranged in the periodic table and each is represented by a symbol.
• The chemical elements are arranged in order of increasing atomic number.
• The horizontal rows on the periodic table are called periods and the vertical columns are called groups.
• The elements in group 1 are known as alkali metals and they react rapidly with water, producing an alkaline solution and hydrogen gas.
• The elements in group 7 are known as halogens and exist as diatomic molecules.
• The elements in group 0 are known as noble gases and are very unreactive, existing as individual atoms (monatomic).
• Atoms are neutral because they have equal numbers of protons and electrons, however, when they lose two electrons they are no longer neutral and change into ions with a two positive charge.
• Alkali names include Sodium hydroxide, Calcium hydroxide, and Lithium hydroxide.
• All alkaline solutions contain more hydroxide ions than hydrogen ions.