Chemistry Year 9 End Of Year Exam, image - Coggle Diagram
Chemistry Year 9 End Of Year Exam
C1: Atomic Structure
Structure Of the Atom
Nucleus and shells: The atom has a central Nucleus and this is surrounded by shells. The radius of an atom is about 0.1nm and the radius of a nucleus is less than 1/10000 of the radius of an atom.
Subatomic Particles: t=The nuclei of all atoms contain subatomic particles, which are protons and neutrons. The outer shells of an atom contain subatomic particles called electrons. The relative mass of a proton is 1, the relative mass of a neutron is one and the relative mass of an electron is very small.
Atomic Number and Mass Number
Atomic Number: The number of protons in an atom in an element is its atomic number.
Mass Number: Atoms of different elements usually have different mass numbers.
Calculating Numbers of subatomic particles: The symbol for an atom can usually be shown by putting its mass number at the top and its atomic number at the bottom.
number of protons = atomic number
number of electrons = atomic number
number of neutrons = mass number - atomic number
Relative atomic mass
Total mass of atoms/total number of atoms
Isotopes: Atoms of the same element must have the same number of protons but they can have a different number of electrons. The same atomic number but different mass numbers.
C2: The Periodic Table
Development of the Periodic Table
Newlands' Octaves: John Newlands arranged the elements into what was know as relative atomic mass.
Mendeleev's periodic table: Mendeleev also arranged his elements in relative atomic mass but did some other things that made his table much more successful. He realized that physical and chemical properties of elements were related to their atomic mass in a repeating or periodic way and so arranged them in a way that groups of elements with similar properties fell into vertical columns in his table.
Electronic structure and the Periodic Table
Electrons in shells occupy energy levels also called electron shells, outside the nucleus. Different shells can hold different maximum number of electrons.The electrons in an atom occupy the lowest available energy level first. This is the shell nearest the nucleus.
Group 1: Alkali metals: Group 1 metals are very reactive. They must be stored under oil to keep air away from them. Group 1 elements form alkaline solutions when they react with water and this is why they are called alkali's. Lithium fizzes steadily when it reacts with water. When sodium reacts with water is melts to form a ball that moves around on the surface and fizzes rapidly. Potassium is added to water and it melts and floats. It moves around quickly on the surface of the water. The metal is also set on fire.
Group 7: The Halogens
Group 7 are all reactive non-metals. They react with metals to form metal halides and with hydrogen to form acidic hydrogen halides. The halogens show their trends in physical and chemical properties.
The halogens become less reactive going down group 7.
Physical Properties: The halogens are simple molecules. A molecule has two atoms joined by a single covalent bond. The melting points and boiling points increase as you go down group 7. The molecules become larger and the bonds become stronger.More energy is needed to break the bonds.
Chemical Properties: Group 7 have 7 electron in their outer shell. Halogens react with metals to produce salts. (Chlorine reacts with sodium) Sodium + Chlorine = Sodium Chloride
Bonding and structure
A covalent bond is a shared pair of electrons, electrostatically attracted to the positive nuclei of two atoms. Atoms can share electrons in order to gain a stable and full outer shell of electrons.
Are usually formed between metal and non metal with a large difference between electronegativity. Eg..Sodium chloride. The Ionic bond is the electrostatic force of attraction between a metal ion and a non-metal ion.