Published on March 2, 2014
GAC 023 GENERAL SCIENCE Refina Ayu Alifa Tsamara Alifia
ION Alifia and Alifa
Basic What is ion? An ion is a charged atom or molecule. It is charged when the number of electrons isn’t equal with the number of protons in the atom or molecule What is atom? singe particle that cant be broken down by chemical reaction. What is molecule? atoms join together to form molecule, only non metals can bond together to form molecules in a chemical bond.
How did it become an ion? Metal atoms and non-metal atoms go in opposite directions when they ionize: Metal atoms lose the electron, or electrons, in their highest energy level and become positively charged ions Non-metal atoms gain an electron, or electrons, from another atom to become negatively charged ions The process of an atom becoming an ion is called ionization.
Positive Ion (Cation) => Occurs when an atom loses an electron (negative charge) => more protons than electrons. Negative Ion (Anion) => Occurs when an atom gains an electron (negative charge) => more electrons than protons.
HOW TO DETERMINE THE CHARGE? The number of charges on an ion formed by a metal is equal to the group number of the metal The number of charges on an ion formed by a non-metal is equal to the group number minus eight Hydrogen forms H+ ions
Group 1 Example element Charge Symbol Of Ion Group 2 Na Mg +1 +2 Group 3 Group 4 Al Co +3 Carbon & Silicon in group 4 usually form covalent bond by sharing electron. Group 5 Group 6 Group 7 Group 0 N O Cl He -1 Don’t react with other element to form ion EXAMPLE Na+ Mg2+ Al3+ Carbon & Silicon in group 4 usually form covalent bond by sharing electron -3 N3- -2 O2- Cl- Don’t react with other element to form ion
Ionic Bond When metals react with non-metals: Electrons are transferred from the metal atoms to the nonmetal atoms, forming ions. The resulting compound is called an ionic compound. The metal atoms become positive ions and the non-metal atoms become negative ions. There is a strong force of attraction between these oppositely charged ions, called an ionic bond
EXAMPLE Na losing an electron & Cl gaining an electron Thus the Na becomes Na+ The Cl becomes Cl-
Covalent Bond O A covalent bond is a strong bond between two non- metal atoms. It consists of a shared pair of electrons. O Covalent bonds are strong - a lot of energy is needed to break them O Atoms may form multiple covalent bonds O There is a quick way to work out how many covalent bonds an element will form. The number of covalent bonds is equal to: 8 - the group number
To see the number of Covalent bond Hydrogen forms 1 covalent bond The noble gases in group 0 don’t form any
Covalent bonds can be represented in several different ways. 1. Straight lines and models 2. Double and triple bonds 3. Dot and cross diagram
Straight and line models • Straight lines are the most common way to represent covalent bonds, with each line representing a shared pair of electrons.
Double and triple bonds • Note that molecules can have a double covalent bond - meaning they have two shared pairs of electrons - or a triple covalent bond - three shared pairs of electrons. • A double covalent bond is shown by a double line, and a triple bond by a triple line. • A molecule of oxygen (O2) consists of two oxygen atoms held together by a double bond, like this: • A molecule of nitrogen (N2) has two nitrogen atoms held together by a triple bond, like this:
Dot – and – cross diagram • Dot-and-cross diagrams are another way to represent covalent bonds. The shared electron from one atom is shown as a dot, while the shared electron from the other atom is shown as a cross. • When drawing dot-and-cross diagrams for covalent bonds, you only need to show the electrons in the highest occupied energy level, as only these are involved.
References http://www.bbc.co.uk/schools/gcsebitesize/science/add_aq a_pre_2011/atomic/ionicrev4.shtml http://www.bbc.co.uk/schools/gcsebitesize/science/add_aq a_pre_2011/atomic/covalentrev3.shtml http://www.chem4kids.com/files/atom_ions.html http://www.qrg.northwestern.edu/projects/vss/docs/propul sion/1-what-is-an-atom.html http://www.microncorp.com/energaire/ions.html
1. 2. 3. 4. 5. 6. 7. What is an Ion? How did an ion became a cation? How did an ion became an anion? Mention 2 examples of Cation and Anion! What is an ionic Compound? What is a covalent bond? Mention three ways to present covalent bonds!
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