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Formation of Ionic Compounds. compound - a combination of different element - can be ionic or covalent. compounds. covalent. ionic. Valence shell In an atom the outermost shell of electrons, the valence shell, determines its interaction with other atoms. Octet rule
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compound - a combination of different element - can be ionic or covalent compounds covalent ionic
Valence shell • In an atom the outermost shell of electrons, the valence shell, determines its interaction with other atoms
Octet rule • all atoms strive to have the same valence shell as their closest noble gas
Lewis symbols • Since how atoms react is dictated by the number of electrons in their valence shell Lewis symbols can be used to draw valence shells, ex. Na
first place electrons, one at a time, at the 12, 3, 6, and 9 o’clock positions, add more electrons by pairing them, one at a time, in the same order as you placed the first four electrons
Formation of Ions • atoms are most stable when their valence shell is full, like that of Noble Gases • they achieve this by gaining or losing electrons, depending on how many they have if they have less than 4 e they will lose them if they have more than 4 e they will gain them
http://jchemed.chem.wisc.edu/JCEsoft/CCA/CCA0/movies/NACL1.htmlhttp://jchemed.chem.wisc.edu/JCEsoft/CCA/CCA0/movies/NACL1.html
ions • atoms that lose or gain an electron are called ions • ions can also be represented by Lewis symbols: the Lewis symbol is enclosed in square brackets, the charge of the ion is placed outside the brackets.
cations • positively charged ions, have lost electrons, ex. Na, • metals lose electrons and become cations sodium atomsodium ion
anions • negatively charged ions, have gained electrons, ex. Cl • nonmetals gain electrons and become anions chlorine atomchloride ion
Ionic bonds form between metals and nonmetals. • since opposites attract, when a cation and anion come into contact, they experience an electrostatic force of attraction, resulting in a chemical bond known as an ionic bond
ionic compounds ex. NaCl -crystals (or crystal salts) of positive and negative ions held together by electrostatic forces (ionic bonds) -they form formula units (not molecules)