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Key concepts in chemistry - Coggle Diagram
Key concepts in chemistry
the structure of an atom Is a nucleus containing protons and neutrons, surrounded by electrons In shells
a proton has a charge of +1, an electron has a charge of -1, and a neutron has a charge of 0
a proton has a mass of 1, a neutron has a charge of 1 and an electron has a charge of nearly 1, (1/1835)
on the periodic table, an element has a mass number and an atomic number
the mass number is the sum of the number of protons and neutrons In the nucleus and Its the number on the top
the atomic number Is the number of protons In the nucleus and Its the number on the bottom
Isotopes are atoms of the same element that contain the same number of protons and electrons but a different number of neutrons
The symbol for an isotope is the chemical symbol (or word) followed by a dash and then the mass number
The relative atomic mass of each element is calculated from the mass number and relative abundances of all the isotopes of a particular element
relative atomic mass formula:
(% of Isotope a x mass of Isotope a) + (% of Isotope b x mass of Isotope b) / 100
the periodic table is arranged in order of atomic mass, in rows called periods. elements with similar properties are placed in the same vertical columns called groups
he predicted the existence and properties of some elements not then discovered because he realised elements with similar properties belonged In the same groups In the periodic table so he left gaps In the periodic table for those elements
metals are elements that react to form positive Ions and most of the elements are metal. they are found to the left and towards the bottom of the periodic table. non metals do not form positive Ions and they are found towards the right and top of the periodic table
the group an electron In tells you how many electrons are In Its outermost shell, e.g. group 1 elements have one element In their outer shell. the period an electron Is In tells you how many shells they have
ionic bonds are formed by the transfer of electrons between atoms to form cations and anions. Ionic bonds are between metals and nonmetals. metal atoms lose electrons to become positively charged Ions (cations) and non metals gain electrons to become negatively charged Ions (anions)
an Ionic compound Is a lattice structure consisting of a regular arrangement of Ions, held together by strong electrostatic forces between oppositely charged Ions
ionic compounds have high melting and boiling points because a lot of energy Is required to break the strong bonds
when melted or dissolved In water, Ionic compounds conduct electricity because the Ions are free to move and carry current, but they dont conduct electricity as solids as the Ions are fixed and not able to move
a covalent bond Is formed when a pair of electrons Is shared between two atoms. It occurs between non metals
simple molecular compounds have low melting and boiling points and weak Intermolecular forces between the molecules. they also do not conduct electricity
giant covalent structures have very high melting points. all the atoms In these structures are linked to other atoms by strong covalent bonds. some giant covalent structures conduct electricity whereas others cannot
metals consist of giant structured of atoms arranged In a regular pattern. the electrons In the outer shell of metal atoms are delocalised and are free to move through the entire structure.
metals have giant structures of atoms with strong metallic bonding, therefore most metals have high melting and boiling points
metals can conduct electricity and heat because of the delocalised electrons In their structures
the layers In metals can slide over eachother so metals can be bent and shaped
metals are Insoluble In water, but some will react with It Instead