Chemistry Reviewby Margaret Zulick

The Atom: makes up everything (living and nonliving)

• Made of – Protons (+)– Neutrons (0)– Electrons (-)

• 2 parts:– Nucleus - inside (protons and neutrons)– Electron Cloud - outside (electrons)• Electrons in outer shell = Valence Electrons

Elements

• Atoms that have the same number of protons are the same element

• Also known as…– “A pure substance” – can’t be broken down

• All elements are displayed on the Periodic Table

The only option that is an element on the periodic table is Gold.All the other options are mixtures or compounds (combinations of other elements that could be broken down).

Periodic Table: organizes all elements

Metals• On the Left and in

the middle• Shiny (luster)• Malleable• Conducts heat &

electricity

Periodic Table: organizes all elements

Non - Metals• On the Right• Dull• Brittle• Bad conductors

Periodic Table: organizes all elements

Metalloids• On the Stairstep• Semiconductors

(computer chips)• Mix of metals and

nonmetals

Based on their location on the PT, determine whether the following

elements are metals, metalloids or nonmetals.

• Fluorine (F)• Potassium (K)• Manganese (Mn)• Silicon (Si)• Nitrogen (N)

Based on their location on the PT, determine whether the following

elements are metals, metalloids or nonmetals.

• Fluorine (F) - Nonmetal• Potassium (K) - Metal• Manganese (Mn) - Metal• Silicon (Si) - Metalloid• Nitrogen (N) - Nonmetal

The Periodic Table is organized!

• Periods :left and right

• Groups: Up and down– Elements in the same group are similar– Alkali Metals: most reactive (Group 1)– Noble Gases: do not react (Group 18)

Nitrogen (N) and Phosphorus (P) are in the same group, so they are the most similar.

The Periodic Table is organized!

Atomic Number = number of protons

Symbol

Element Name

Atomic Mass

Bonds• Atoms bond because they want a full outer shell– The closer they are to having a full shell, the more

reactive they are (more likely to bond)

Bonds hold atoms together to form a compound

When atoms of different elements bond, they form compounds

• Examples:1. H + O H2O

Hydrogen + Oxygen Water

2. Na + Cl NaCl Sodium + Chlorine Sodium Chloride

• Compounds are completely different than the elements that make them up!

Chemical Equations

What starts the reaction(ingredients)

What is made after the reaction

Subscript: Tells us the number of atoms

Coefficient: used to balance equations

Law of Conservation of Mass

Mass can never be created nor destroyed

Need the same number of atoms of each element on each side!

Mass or matter cannot be created nor destroyed!

Mass cannot be created nor destroyed.What you start with, you MUST end with!

To speed up a reaction…

• Add heat

• Add a Catalyst

• More surface area – smaller pieces are better than big pieces.

X ✔

Mixtures

• When 2 or more compounds are mixed together, we call this a mixture.

Ex. H2O and NaCl mixed together forms a salt water mixture

• 2 Types:– Homogeneous: The same throughout

(ex. Lemonade/Koolaid)– Heterogeneous: NOT evenly mixed

(ex. Salad: you see lettuce, peppers, tomatoes, salad dressing)

HomogeneousHeterogeneous

Solute vs. Solvent vs. Solution• Solution = Homogeneous Mixture

• Solute: Solid that is dissolved– Ex. Koolaid Powder

• Solvent: Liquid the solid is dissolved into– Universal Solvent is WATER!

Concentration

• High Concentration: Lots of solute dissolved in solvent– Ex. LOTS of Koolaid powder in a little bit of water,

makes it very strong and concentrated

• Low Concentration: Little bit of solute in solvent– Ex. Small amount of Koolaid in water makes it

taste weak, low concentration

Chemical Change

• Cannot be undone• Makes a BRAND NEW substance!

• 4 Signs:– Color Change– Formation of a gas– Formation of a precipitate (a solid)– Temperature Change

Physical Change

• Can be undone• Does NOT change what the substance is

• Ex. Tearing a piece of paper• Phase changes (solid to liquid, liquid to gas)– Ex. Melting ice into liquid water

Freezing Water = still water! = PhysicalBurning Coal = cannot undo this = Chemical

Exothermic Vs. Endothermic

• Exothermic: – Exo = OUT!

Heat RELEASED = will feel warm

• Endothermic:– Endo = IN!

Heat absorbed in = will feel coldEx. Photosynthesis

pH Scale• Scale of 0 to 14

• Acids: Sour (ex. Orange Juice, Vinegar)pH between 0 and 7

• Bases: Bitter (ex. Milk, detergent)pH between 7 and 14

• Neutral pH is 7