Atoms and elements

• An atom consists of a nucleus and electronic shells.
• The Nucleus of an atom consists of subatomic particles called protons and neutrons.
• The electronic shells consists of a subatomic particle called the electron.
• In a neutral atom, the number of protons equal the number of electrons.
• In an ion, the number of protons DO NOT equal the number of electrons.
• Protons have a positive charge.
• Neutrons have no charge and are hence neutral.
• Electrons have a negative charge.
• A positive Ion is caused by a loss of electrons and is called a cation.
• A negative Ion is caused by an excess of electrons and is called an anion.
• The Atomic mass is the sum of number of neutrons and protons in the nucleus of an atom.
• The Atomic number is the number of protons in an atom.
• The Atomic mass number is always larger than the Atomic number.
• The Atomic mass number is also known as the nucleon number.
• The first electronic shell can store 2 electrons and is known as shell K.
• The second electronic shell can store 8 electrons and is known as shell L.
• The third electronic shell can store 8 electrons and is known as shell M.
• The fourth electronic shell can store 18 electrons and is known as shell N.
• The mass of a proton is 1
• The mass of a neutron is 1.
• The mass of an electron is 1/1840 and is considered negligible.
• In the periodic table, group 1 metals are known as alkali metals.
• In the periodic table, Group 2 metals are known as Alkali Earth metals.
• In the periodic table, the block between groups 2 and 3 is known as transition elements.
• In the periodic table, group 7 are halogens
• In the periodic table, group 8 or 0 are Noble gases.
• Isotopes are atoms of the same element with different neutron, but same proton number.
• Isotopes still have the same Atomic number but a different Atomic mass.
• Isotopes of the same element display the same chemical characteristics because they have the same number of electrons and protons.
• Because of the difference between Atomic masses, Isotopes of the same element have differences in their density, boiling point and melting point.
• The amount of electrons in the outermost shell of the atom Is the group number of the element.
• Atoms can gain or lose electrons to form negative or positive ions
• Ions are formed when an atom gains or loses one or more electrons.
• A mass spectrometer is an instrument in which atoms or molecules are ionized and then accelerated, and then the ions are separated according to their mass.
• Groups 1,2 and 3 are metals except boron.
• Groups 4-7 are non metals.