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Chemistry C1 unit 1
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- 11.1 Atoms, elements, and compounds- There are about 100 different elemtents of which all things are made
- The periodic table list' these elements
- Each element is made of one type of atom
- Every element has a representation as a chemical symbol e.g. Gold: Au
- In a periodic table the elements are organised in columns, called groups. Elements in the same group usually have similar properties.
- Atoms have a tiny nucleus surrounded by electrons
- When elements react they form together with other elements to create compounds.
- A compound is formed when two or more elemnts combine together. - 21.2 Atomic structure- The nucleus of an atom contain two types of particles, protons and neutrons.
- Protons have a posotive charge
- Neutrons have no charge
- Electrons are tiny negatively charged particles, that move around the nucleus.
- An atom has no overall charge because:
Electron: -1
Protons: +1
Neutrons: 0
Therefore the overall charge is 0
- The atomic number is the number of protons in an atom. All atoms of the same element has the same atomic no.
- mass number= protons + neutrons - 31.3 The arrangment of electrons in atoms- each electron in an atom is in a shell.
- Electrons with the lowest energy level in the shells nearest the nucleus. (and vise versa)
- elements in the same group, have the same number of electrons in their outer shells
- group 1 elements react quickly with water and oxygen
- group 1 elements are all reactve, the lower you go down the group the more reactive the elements become e.g. Potassium is more reactive than Lithium
- Atoms of the ureactivenoble gases (group 0) have very stable electron arrangements e.g. Krypton: 2-8-8-8-8-2 - 41.4 Forming bonds- When different elements react together they form compounds
- metal + non-metal -> ions are formed
- metal atoms lose one or more electrons to form posotively charged ions
- non metals gain electrons to form negatively charged ions
- The oppositily charged ions attract each other strongly, and the compound then has ionic bonds.
- The chemicle formula of a compound shows us the simplest ratio of elements in a compound. E.g. NaCl shows us that an equal number of Na atoms were used as Cl atoms.
- When non-metals react their atoms share electrons and form covalent bonds. These are molecules
- The chemical formula of a compound/molecule shows us the number of atoms that partook in the reaction. e.g. H20 shows us 2 hydrogens and an oxygen atom. - 51.5 Chemical equations- In chemical reactions the atoms that form the reactants re-arrange themselves to form the products
- In a chemical reactions atoms are not created nor are they destroyed
- The number and type of atom shouldbe the same before and after the reaction.
- The mass of the the reactants = mass of products
- Symbol equations, when written should always be balanced.
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- GCSE (Chemistry) Science Fichas sobre Chemistry C1 unit 1, creado por Tom Fitzgerald el 04/04/2015.
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- Tom Fitzgerald
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