Unit 2 - Chemistry and Introduction To Particles

Particle Theory:

Matter is made up of tiny particles

Each substance has its own kind of particle

The spaces between the particles are larger than the particles themselves

Particles are always in motion. The more energy particles have, the faster they move. Heated particles move faster than colder particles.

Particles that are spaced out from one another have a smaller force.

Classification of Matter

Physical and Chemical Properties

A physical property is a characteristic of a substance that can be determined without changing the composition of that substance.

It may be qualitative or quantitative.

Qualitative: Not measured, often observations. (luster, viscosity)

Quantitative: Analytical observations.

A chemical property is a property of a substance that describes its ability to undergo changes.

I.e. flammability, reactivity

Density

Density Triangle

M

D V

Using Water Displacement to find Volume

Volume of Object = Final Water Volume - Initial Water Volume

Density = Mass/Volume

Physical Vs Chemical Change

Physical Change: No new substance has formed, does not change chemical composition. (still the same substance)

Usually reversible

I.e. Ice melting, water evaporating.

Chemical Change: One or more substances have been formed, and the identity/chemical composition of the substance changes. There are different kinds of chemical changes.

A new substance has formed

Usually not reversible

Iron rusting, burning wood.

Endothermic Changes

Absorb heat from surroundings

Energy is required to occur

I.e. photosynthesis (absorbing sunlight)

Exothermic Changes

Release heat to surroundings (exit!)

Energy is released as a product of the reaction

I.e. Combustion (burning stuff)

Precipitates

Solid particles that form at the bottom after a chemical that are heterogeneous to the solution.

I.e. silver nitrate and potassium chloride

Periodic Trends:

Metals: SLHEMD

Found on the left and central parts of the periodic table; typically solid with a shiny luster.

Conduct heat and electricity, and are malleable (how strong before it breaks) and ductile (can make into wires).

Non-Metals: GDOB

Found in the upper right of the periodic table; mostly gasses or dull solids.

Do not conduct heat or electricity; bromine is the only liquid non-metal.

Metalloids: Behave like both nonmetals and metals.

Are in a stair location on the table, separating metals and non metals.

May or may not conduct electrical or thermal energy.

Alkali Metals 1SLR

First column from left, referred to as group 1 elements.

Low density, soft

Highly reactive in water because of its one valence electron.

(valence electrons are on the outside ring, and are prone to reactions)

I.e. Lithium (Li), Sodium (Na) and Potassium

Alkali Earth Metals

More Natural and have a less reactivity rate and are harder

Noble Gases 18USH

Column on far right.

Stable, unreactive.

I.e. Helium, Neon

Group 18

Halogens 17RCSE

Very Reactive

Group 17, left of noble gasses.

Form compound with alkali metals

Used especially in salt formations

Rarely found in elemental form.

Can be poisonous in small amounts (i.e. chlorine gas)

I.e. Iodine (used in sanitizer), bromine (used to better battery life of lightbulb) and chlorine (used to clean pools)

Rows on the periodic table are known as periods.

They refer to cycles.

Show an increase or decrease in reactivity.

History of the Atom

Democritus 400 BCE IDMS

Proposed the atom

They are indivisible (false)

They are different sizes.

In constant motion.

Separated.

John Dalton 1805 IFEDICD

Matter is made up of tiny indivisible particles called atoms (false)

All atoms of an element are identical

Atoms of different elements are different

Atoms can be rearranged to form new substances.

Atoms cannot be created or destroyed.

Thomson 1897

Existence of + and - particles in the atom

Negative charges are spread throughout a positive space.

Charges balance out

Plum Pudding

Did not include nucleus dummy

Rutherford

Gold foil experiment

Positively charged particles were shot at a gold foil sheet. Most particles went through because particles have empty space, but some deflected due to the nucleus.

Also discovered the nucleus as a result.

Chadwick 1932

Planetary model

Explained mass, relative charge and gave symbols.

Neil Bohr 1913

Creating orbital model

Using rutherford's knowledge as well

2 electrons on the first ring, and 8 on second and third.

Gilbert Lewis Newton

Made the Lewis dot diagram

Subatomic Particles and Calculating Neutrons

Electron: Negatively charged and located on outer rings

Valence Electrons: On the outer shell

Proton: Positively Charged and located in nucleus

Atomic Number is the number of protons.

PROTONS AND ELECTRON # STAYS SAME

Neutron: Relative charge of 0.

Used to bind nuclei together and to balance electrons from protons.

To calculate neutrons

Atomic Mass (Rounded) - Atomic Number (Sequence) = # of Neutrons

Bohr Rutherford Diagrams

Proton and Neutron Number shown on circle at the center (representing nucleus)

Surrounding shells

Go by 2 electrons, 8 electrons, ctd..

Electrons are on the outer shells

Atoms, Molecules and Compounds

Atoms: Are a kind of particle that is the basic building block of all matter

Molecule: Combination of two kinds of atoms (Can be same or different).

Compound: A type of molecule where atoms can be broken down.

Elements: Are a pure substance made up of one kind of atom (cannot be broken down)

Lewis-Dot Diagrams

Represent the Valence Electrons

Each dot represents a valence electron.

Ionic Bonds

Formed when atoms transfer electrons from one to another.

Typically occurs between a metal and a nonmetal.

Covalent Bonds

Formed when atoms share electrons

Occurs between nonmetals only.

H O F BR I N CL

Diatomic Elements

Pure elements that are form molecules by two atoms connected together