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- 1- All substances are made up of atoms. - Elements contain only one type of atom. - Compounds contain more than one type of atom. - An atom has a tiny nucleus in its centre, surrounded by electrons.- Atoms are made of protons, neutrons and electrons.
- Protons and electrons have equal and opposite electric charges. Protons are positively charged, and electrons are negatively charged.
- Neutrons have no electric charge. They are neutral.
- Atomic number
= number of protons
(= number of electrons)
Mass number = number of protons + neutrons.
- Atoms are arranged in the periodic table in order of their atomic number. - 2- The electrons in an atom are arranged in energy levels or shells. - Atoms with the same number of electrons in their outermost shell belong in the same group of periodic table. - The number of electrons in the outermost shell belong in the same group of the periodic table. - The number of electrons in the outermost shell of an element's atoms determines the way that element reacts. - The atoms of the unreactive noble gases (in Group 0) all have very stable arrangements of electrons.Lithium + water ---> Lithium hydroxide + hydrogen
Sodium + water ---> Sodium hydroxide + hydrogen - 3- When atoms from different elements react together they make compounds. The formula of a compound shows the number and type of atoms that have bonded together to make that compound. - When metals react with non-metals, charged particles called ions are formed. - Metal atoms form positively charged ions. Non-metal atoms from negatively charged ions. These oppositely charged ions attract each other in ionic bonding. - Atoms of non-metals bond to each other by sharing electrons. This is called covalent bonding.- As no atoms are ever created or destroyed in a chemical reaction:
The total mass of reactants = the total mass of products.
- There is the same number of each type of atom on each side of a balanced symbol equation.
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- Chemistry Flashcards on Untitled, created by helenazecevic on 11/05/2013.
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