Foundations of Chemistry Chp. 1 PDF

Preview

Summary

Instructor: Weber, A...

Description

Foundations of Chemistry Friday, January 5, 2018

1:15 PM

What is Chemistry? - Science concerned with structure and behavior of matter - Everything ○ The universe is composed of matter and energy ○ Matter is anything that has mass and takes up space ○ Matter is made up of small particles called atoms How to describe all this matter and energy? - Use a model for a simplified version of reality - For example a map, globe, idea etc Kinetic Molecular Theory - All matter is composed of tiny particles - The particles are in constant motion - Increased temperature reflects increased motion of particles - Solids, liquids and gases differ in freedom of particles and in how strongly the particles attract each other Solids 1. 2. 3. 4. -

-

Friction of moving particles causes temperature to rise As temperature rises, particles move faster and bump harder Neighboring particles are pushed further apart and the solid expands If lubricating or cooling system fails, engine expansion may cause a piston to jam into cylinder moving particles bump and tug one another but stay in the same small space

Shape and volume: Constant shape and volume Arrangement: The particles are constantly moving, colliding with other particles and changing direction and velocity Attraction: Each particles is trapped in a small cage, whose walls are formed by other particles that are strongly attracted to each other ○ About 70% of space occupied by particles, 30% empty

Liquids

test onceive a model

Observation refine

-

Particles move fast enough for attractions to be constantly broken and reformed Particles are less organized with slightly more space between them, than a solid Particles move throughout the container

-

Shape and volume: Constant volume but variable shape Arrangement: The particles are moving fast enough to break the attractions between particles that form the walls of the cage that surround particles in the solid form Thus each particles in a liquid is constantly moving from one part of the liquid to another (diffusion) ○ About 70% of space occupied by particles, 30% by space

-

Evaporation

Gases -

Because particles are so far apart, there is usually no significant attraction between them Particles move in straight paths changing direction and speed when they collide

-

Shape and volume: Variable in shape and volume Arrangement: Large average distances between particles Attraction: Little attraction between particles Constant collision between particles, leading to constant changes in direction and vel ○ About 0.1% of space is occupied by particles, 99.9% empty space

-

Elements - Consider the separation of the components of water by distillation

ity

-

Building blocks of matter Cannot be chemically converted into other substances Each element is known by name, atomic symbol and atomic number

Metals, Non-metals and Metalloids Characteristics of Metallic Elements - Metals have a shiny metallic luster - Metals conduct heat well and condu currents in solid form - Metals are malleable ○ For example; gold; can be ham sheets without being broken

Atoms - The smallest part of an element that retains the chemical characteristics of the eleme - All matter is made up of atoms - Atoms are made up of 3 subatomic particles - The number of each subatomic particle in atom determines the chemical characterist

t electrical

mered into tiny

t itself

s

The Subatomic Particles - Distinguished by charge, location and mass

Particle Number Rules - # of protons = atomic number - For uncharged atoms: # of electrons = # protons - # of neutrons = (mass #) - (# of protons) ○ Ex. Mass = # of neutrons + # of protons - Question: How many of each subatomic particles are found in C, Al and Co? ○ C: 6=protons, 6=electrons, mass is 12-6 protons = 6 neutrons ○ Al: 13=protons, 13=electrons, mass is 27-13 protons = 14 neutrons ○ Co: 27 protons, 27 electrons, mass 59-27 protons = 32 neutrons Ions and Isotopes - Isotopes: atoms that have the same atomic number but different mass numbers ○ Ex. 120Sn and 119Sn are isotopes - Question: How many neutrons do they each have? ○ 120Sn: z=50, #p=50, (120-50)=#n 70 ○ 119Sn: z=50, #p=50, (119-50)=#n 69 - Ions: Atoms that carry electrical charge due to the gain or loss of electrons - Cations: have an overall positive charge having lost one or more electrons - Anions: have an overall negative charge having gained one or more electrons - Question: How many protons, neutrons and electrons in Mg2+,

-Isotopes

Ca2+ and Br-. ○ Mg2+: z=12, #p=12, (24-12)=12 #n, since its plus 2, must be #e= 10

Elements, Compounds and Mixtures - Element: a substance that cannot be chemically converted into simpler substances; a which all of the atoms have the same number of protons and therefore same chemica characteristics - Compound: a substance that contains two or more elements, the atoms of these elem combining in the same whole number ratio - Mixture: a sample of matter that contains two or more pure substances (elements an compounds) and has variable composition

Bonding - An unpaired electron has a higher potential energy than a paired electron - Systems naturally tend to lowest

Covalent Bonds - Form between two non-metals - Electrons are shared in a chemical bond - Covalently bound atoms are

Io

ubstance in

nts always

c Bonds Form between non-metal and a metal There is a complete transfer of electrons from one atom to another The two atoms are held together by electrostatic

potential energy state (just like how a ball rolls down a hill)

-

referred to as molecules Equal sharing = non polar covalent Unequal sharing = polar covalent proportionate to the difference in electronegativity's between bonding atoms

Lewis Structures • Electron dot symbols- shows valence electrons • Nonbonding pairs of valence electrons are called lone pairs

•

Step 1. 2. 3. 4.

• • Ionic compounds will transfer e- from metal to non -metal so that one atom (metal) has zero e- and the non metal has 8e• For now we will focus on covalent bonded molecules • Atoms in a molecule exhibit "common bonding patterns'

Chemical Nomenclature - Covalently bonded molecules - Ionic compound 1. Main group metal 2. Transition metals 3. Polyatomic ions Formula notation

-

interactions Ionically bound atoms are called ionic "compounds" Metal is always positively charged Non metal is always negatively charged

for drawing Lewis Structures Determine the # of valence eDraw a "skeleton structure, place the atom that can form the most bonds in the center Place all other atoms around the center atom Use lone pairs of electrons and double and triple bonds to satisfy the common bonding pattern and octet rule Question: Draw the Lewis structures of H2, O2, and N2 including lone pairs? ○ H-H = ○

O2 =

○

N2 =

Question: Draw Lewis Structures of NH3, H2O, PCL3, CH2O and CO2?

-

Formula notation ○ The subscript is used to indicate the number of atoms of that type in the molecu outside parentheses apply to each atoms in parentheses, ○ For example; the molecule N2O4 has 2 nitrogen's and 4 oxygens atoms

Prefixes 1-mono 2-di 3-tri 4-tetra 5-pent

6-hex 7-hept 8-oct 9-non 10-dec

Covalently bonded molecules: formula to name - Write 1st atom then 2nd atom using "ide" - Prefixes used to indicate how many of each atoms - Leave out "mono" on the first atom

Question: Determine the names of the covalently bonded molecules with formulas: Page 2 Question: given the name/formula of the covalently bonded molecule determine the formula the compound: carbon dioxide, sulfur dichloride, BF3, P4O3, CS2? Naming of Ionic Compounds with Main Group Elements - Metal (cation) goes first - Non-metal (anion) goes second and ends with "ide" - Atoms will combine in a way that forms a neutral compound so no prefixes necessary ○ Non metallic form anions in order to get the same number of electrons of the n stability noble gas ○ Similar groups 1, 2 and 3 lose enough electrons to achieve stability of nearest n ○ Page 3 Naming Ionic Compounds with Transition Metals - Metal will loses e- to form cation - B group metals can have variable charge - Charge on non-metal will determine charge on metal - No prefixes - Metal is named first and non-metal second ending with "ide" - Charge on metal is indicated with Roman numeral - Pg 4 Naming of Ionic Compounds with Polyatomic Ions - Memorize this table - Metal name first and non metal second ending with "ide" - Pg 5

. Subscripts

name of

rest high ble gas

•...