Physical Science Coach Mynhier Chapter 6: Physical Science Coach Mynhier

Lesson 1: Compounds and Molecules What are Compounds? Table salt is an example of a compound. It is made of the two elements sodium and chlorine. When two elements combine to form a compound the compound has properties very different from the elements that make it.

Chemical Bonds Distinguish Compounds from Mixtures Chemical Bond: the attractive force that holds atoms or ions together. In a mixture substances are just placed together. Each substance in the mixture retains its own properties. When substances are chemically bonded they form something new with completely new properties.

A Compound Always has the Same Chemical Formula The chemical formula for water is H2O. The chemical formula for table sugar is C12H22O11. Table salt is NaCl. A chemical formula tells you the types and how number of atoms making up the simplest unit of a compound. Water in a comet in space or water in your cells will always be H2O.

Chemical Structure Shows the Bonding Within a Compound Water’s chemical formula tells us what an atom is made of, it does not tell us anything about the way these molecules are arranged. Chemical structure describes the arrangement of atoms in a substance.

Two Terms are used to Specify the Positions of Atoms Relative to One Another in a Compound. Bond length: gives the distance between the nuclei of two bonded atoms. Bond Angles: when a compound has three or more atoms, this tells you how they are oriented in space.

Models of Compounds Ball and Stick Model: helps us to “see” a compounds structure. Structural Formula: mostly the same as a Ball and Stick Model except that the chemical symbols is used. Space-filling Models: shows the space that is occupied by the atoms. Harder to see bond lengths and angles.

How Does Structure Affect Properties? Compounds with network structures are strong solids In quartz crystals, SiO4, Every Si atom is bonded to 4 oxygen atoms. These bonds are strong and hard to break and allow for high melting points and high boiling points.

Some Compounds are Made of Networks of Bonded Ions. Like quartz, table salt, NaCl, is found in the form of regularly shaped crystals. Crystals of salt are cube shaped. The network is made of tightly packed, positively charged sodium atoms and negatively charged chloride atoms. This causes relatively high melting points and boiling points.

Some Compounds are Made of Molecules Salt and Sugar are very similar. Unlike salt, sugar is made up of molecules. A molecule is made up of carbon, hydrogen, and oxygen (C12H22O11). These molecules do attract each other, not as strongly as the bonds between the C, H, O.

Attractions between water molecules are called hydrogen bonds. These bonds give water its “elasticity.” There is a weak attraction that holds each of these H2O molecules together. That is why belly flops hurt.

Lesson 2: Ionic and Covalent Bonding Atoms bond when their valence electrons interact. Generally, atoms join to form bonds so that each atom has stable e- configuration. (8 e-) Bonds can bend and stretch without breaking Anion: an ion that has a negative charge Cation: an ion that has a positive charge

Lesson 2: Compound Names and Formulas Naming Ionic Compounds In many cases, the name of the cation is just like the name of the element from which it is made. When an atom of Na loses an e-, it becomes a sodium ion, Na+. When a calcium atom loses two e-, it becomes Ca2+.

Ions of Group 1 elements have 1+ charge. Names of Anions are Altered Names of Elements Just like cations, anions of elements in the same group of the periodic table have the same charge. Drop the suffix and add –ide. NaF is made up of sodium ions, Na+, and flouride ions, F-. Therefore, it’s name if Sodium Flouride.

Some Cation Names Must Show Their Charge Consider FeO and Fe2O3 . By the rules we just learned, both would be Iron Oxide. They can’t have the same name, they are different compounds! FeO is a black powder. Fe2O3 is a rust. Some of the transition metals can form different charges. In these cases, a Roman numeral must follow the element.

Weird Cations (continued) Fe2O3 would be Iron (III) Oxide. FeO is Iron (I) Oxide The Roman Numeral indicates the charge on Iron.

POLYATOMIC IONS ACT JUST LIKE ANY OTHER NEGATIVE ION WHEN BONDING IONIC BONDING POLYATOMIC IONS ACT JUST LIKE ANY OTHER NEGATIVE ION WHEN BONDING Na SO +1 -2 4

IONIC BONDING Na SO 2 4 SODIUM SULFATE

IONIC BONDING Al NO +3 3 -1 Al NO 3 1 ( ) 3

Naming Covalent Compounds Mono= 1 Di= 2 Tri= 3 Tetra= 4 Penta= 5 Hexa= 6 Hepta= 7 Octa= 8 Nona= 9 Deca= 10 Prefixes and Number of Atoms

Naming Covalent Compounds Covalent compounds consist of Two non-metals hit the sound icon

Prefixes-stand for the amount of atoms present 1-- mono 2-- di 3-- tri 4-- tetra 5-- penta 6-- hexa 7-- hepta 8-- octa 9-- nona 10-- deca

2 Steps to Naming Covalent Compounds Name the first non-metal.

If there is only one atom present DO NOT use a prefix. If there is more than one atom present then you must use the correct prefix.

Examples: CO2 N2O5 Dinitrogen Carbon Mono= 1 Di= 2 Tri= 3 Tetra= 4 Penta= 5 Hexa= 6 Hepta= 7 Octa= 8 Nona= 9 Deca= 10 Examples: CO2 Carbon N2O5 Dinitrogen

Coach Mynhier’s Awesome Science Class 2. Name the second non-metal using the correct prefix and an -ide ending Coach Mynhier’s Awesome Science Class

N2O5 Examples: CO2 Dinitrogen Pentoxide Carbon Dioxide Mono= 1 Di= 2 Tri= 3 Tetra= 4 Penta= 5 Hexa= 6 Hepta= 7 Octa= 8 Nona= 9 Deca= 10 Examples: CO2 Carbon Dioxide Dinitrogen Pentoxide N2O5

Cl2O You try . . . Mono= 1 Di= 2 Tri= 3 Tetra= 4 Penta= 5 Hexa= 6 Hepta= 7 Octa= 8 Nona= 9 Deca= 10 You try . . . Cl2O

Cl2O You try . . . Dichlorine monoxide Mono= 1 Di= 2 Tri= 3 Tetra= 4 Penta= 5 Hexa= 6 Hepta= 7 Octa= 8 Nona= 9 Deca= 10 You try . . . Cl2O Dichlorine monoxide

CO Carbon Monoxide Phosphorus Trichloride PCl3 Carbon Tetriodide CI4

Writing Molecular Formulas Phosphorous Trichloride PCl3

N3 Trinitrogen CCl4 Carbon Tetrachloride