Study flashcards Elements Polyatomic ions: be sure to learn the chemical formula AND the charge 1of 29
Write the formula for: 1. Phosphate PO 4 3 2. Nitrate NO 3 3. Carbonate CO 3 2 4. Sulfate SO 4 2 5. Ammonium NH 4 + 2of 29
What is the correct formula for the phosphate ion? A. PO 3 2 B. PO 4 2 C. PO 3 3 D. PO 4 3 3of 29
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Ionic Bonds: electron transfer from metal to non metal ions opposites attract Metallic Bonds closely packed cations in a sea of valence electrons 5of 29
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8.1 Molecular Compounds These toy models are made from circular pieces joined together in units by sticks. Atoms can also be arranged in different ways to make a variety of products. 7of 29 Copyright Pearson Prentice Hall
Covalent Bonds: The sharing of electrons The octet rule is the driving force behind how they bond In forming covalent bonds, electron sharing occurs so that atoms attain the electron configuration of noble gases Form from non metals bonded to other non metals 8of 29
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8.1 Molecular compounds/covalent Bonds Molecules are neutral groups of atoms held together by covalent bonds which involve the sharing of electrons Diatomic molecules A compound consisting of two atoms held together by covalent bonds. 7 elements form diatomic molecules in nature: Learn them! 10 of 29
Diatomic molecules: LEARN THEM Hydrogen, the halogens, nitrogen, oxygen (form an upside down L on the periodic table): H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 11 of 29
Properties of molecular compounds relatively lower melting points than ionic compounds may be gases, liquids or solids at room temperature poor conductors of electricity 12 of 29
8.1 Molecular Compounds > Molecules and Molecular Compounds A compound composed of molecules is called a molecular compound. Water and carbon monoxide are molecular compounds. 13 of 29 Copyright Pearson Prentice Hall
Types of covalent bonds Single covalent bond 1 pair of electrons is shared between 2 atoms Double covalent bond 2 pairs of e are shared between 2 atoms Triple covalent bonds 3 pairs of e are shared between 2 atoms 14 of 29
8.1 Molecular Compounds > Molecules and Molecular Compounds 15 of 29 Copyright Pearson Prentice Hall
8.1 Molecular Compounds > Molecules and Molecular Changes Ethane, a component of natural gas, is also a molecular compound. 16 of 29 Copyright Pearson Prentice Hall
Molecular formulas Show how many atoms of each element a molecule contains C 2 H 6 contains 2 carbon atoms and 6 hydrogen atoms Structural formulas Show the arrangement of atoms and bonds in molecules Covalent bonds are represented by dashes Structural formulas are also called Lewis structures 17 of 29
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8.1 Molecular Compounds > Molecular Formulas Formulas of Some Molecular Compounds 19 of 29 Copyright Pearson Prentice Hall
Example: NH 3 Draw the electron dot structure for N and H. Then draw three H atoms around the N atom with three single covalent bonds, so that each atom has a full valence shell of e s 20 of 29
Pairs of electrons that are not shared can be called: unshared pairs lone pairs nonbonding pairs 21 of 29
Steps for drawing Lewis structures 1. Count all of the valence electrons in the compound. 2. Place an electron pair in each bond around the central atom. 3. Complete the octets of atoms bonded to the central atom. 4. Place any additional electrons around the central atom. 5. Form double bonds if the central atom has less than 8 electrons. 22 of 29
Example: Draw a Lewis structure for CF 4 1.Step 1: C: 4e x 1 atom = 4e F: 7e x 4 atom = 28e Total = 32e 23 of 29
2. Step 2 24 of 29
Step 3 (24 e left) 25 of 29
8.1 Section Quiz. Compared to ionic compounds, molecular compounds tend to have relatively A. low melting points and high boiling points. B. low melting points and low boiling points. C. high melting points and high boiling points. D. high melting points and low boiling points. 26 of 29 Copyright Pearson Prentice Hall
8.1 Section Quiz A molecular compound usually consists of A. two metal atoms and a nonmetal atom. B. two nonmetal atoms and a metal atom. C. two or more metal atoms. D. two or more nonmetal atoms. 27 of 29 Copyright Pearson Prentice Hall
8.1 Section Quiz A molecular formula shows A. how many atoms of each element a molecule contains. B. a molecule's structure. C. which atoms are bonded together. D. how atoms are arranged in space. 28 of 29 Copyright Pearson Prentice Hall
Read 8.2 WS: Practice problems, due Mon. GRSW now due next Thurs. 29 of 29