1. The Atom and the Periodic Table
Chemistry
The Atom and the Periodic Table

2. A Picture of an Atom Most of an atom is empty space!
The nucleus contains most of the mass of the atom
The # of protons = the # of electrons (in a neutral atom)
The # of protons determines which element the atom is
The number of neutrons can change – this is called an isotope
Some elements can lose an electron(s) (become positively charged) or gain an electron(s) (become negatively charged) – charged atoms are called ions

6. Atomic Mass = # of protons + average # of neutrons

8. Family or Group
Period
# of valence electrons

9. Electrons are placed in specific electron shells
Electrons are placed in specific electron shells. Each period number equals the number of electron shells in the atom, which stays the same for all the elements in each period

10. Elements in a group or family have similar properties (characteristics) and undergo the same type of chemical reactions (due to having the same number of valance electrons)
Elements across a period change in a regular way (the # of protons increases as does the #of electrons and the atomic mass), but the number of electron shells stays the same

11. Properties of Matter

12. All Pure Matter has Physical Characteristics
Can observe without changing into a new substance
Examples: boiling point, freezing/melting point, hardness, color, texture, & state at room temperature (gas, liquid or solid), density, solubility (if possible) in water or non-polar solvent
If a metal: luster, malleability, conductivity of electricity and heat, attraction to magnet

13. If matter undergoes a physical change, then it is the same substance with the same physical and chemical properties

14. Example: an ice cube, liquid from the faucet, and steam from a boiling pot are all water.
Each state has the same chemical formula, freezing/melting and boiling points, clear color, and is the universal solvent.

15. All Pure Matter has Chemical Characteristics
Can’t be observed just by looking at it
Describes ability to turn into a new substance
To observe the property, the substance MUST react with another and form other pure substance(s), SO there must be a chemical reaction
Examples: flammability, reacts with gas (iron to form rust, copper turns green, silver tarnishes), reacts with metals (acids)

16. If matter undergoes a chemical reaction, there is a new substance with its own physical & chemical properties

17. Sodium (Na) - soft, silvery metal that explodes in water
Chlorine (Cl) - a poisonous yellow-green gas.

18. Chemical Reaction: sodium chloride (NaCl)
a white solid
dissolves in water without exploding
safe to eat – table salt
melting point of 801°C (Na 97.85°C)
boiling point of 1413°C (Cl -34.6°C).

19. Mixtures

20. Compounds vs. Mixtures
A compound is a pure substance made of 2 or more atoms (molecule) that reacted chemically and has unique chemical properties of its own.
A mixture is made of 2 or more substances that do no react chemically, and retain their chemical properties.

21. Types of Mixtures
Heterogeneous – no matter how well mixed, you can still see the separate parts
Example – salad: lettuce, tomatoes, croutons, etc.; can pick out the cucumber slices if you don’t like
Homogeneous – parts are so evenly mixed, you can’t see the different parts; looks like one substance
Example – teaspoon of sugar stirred into hot tea; can’t see sugar but the tea tastes sweet.

22. What is another name for homogeneous mixture?
Solution – a well-mixed mixture
At least one substance dissolves into another
Solute – substance dissolved into the 2nd substance (smaller amount)
Solvent – substance that surrounds the 1st substance (larger amount)
Solubility is a measure of how much solute goes into solvent at a given temperature – this is a physical property

24. Are all solutions a solid dissolving into a liquid?
Liquid into liquid
Gas into gas
Gas into liquid
Solid into solid
Anti-freeze: ethylene glycol into water
Oxygen in air
Oxygen in water, CO2 in soda water
Alloys: metal in metal such as bronze (Sn in Cu), brass (Zn in Cu), 14 kt gold (Ag, Cu, or Zn in Au)

25. Factors That Affect Solubility
Temperature
Pressure
Solvent compatibility

26. Temperature Affects Solubility
↑ solid’s solubility by ↑ temperature, genetally
generally

27. ↑ gas’ solubility by ↓ temperature

28. Pressure Affects Solubility
↑ gas’ solubility by ↑ pressure over the solvent

29. Solvent Compatibility - Like Dissolves Like
Polar solvent + ionic compound
Water is a polar molecule: (+) & (-) sides
Salt is an ionic compound
The sodium ion (Na+) is attracted to water’s (-) side
The chlorine ion (Cl-) is attracted to water’s (+) side.

30. Polar Solvent + Polar Solute
Polar ammonia molecules dissolve in polar water molecules.
The +H of the water molecule is attracted to the –N of the ammonia molecule AND…
The +H of the ammonia molecule is attracted to the –O of the water molecule

31. Non-polar + non-polar Even if a substance is soluble, it may
not dissolve in water
Non-polar: no (+) & (-) parts of molecule
Acetone is a solvent that is partially polar
The components in nail polish are non-polar
chemicals (resins) dissolved in acetone
Letting your nails dry means allowing the solvent to evaporate leaving the resin behind.
To remove, the polish needs to dissolve
This is the same reason you can’t clean oil-based paint from a paint brush using water. You must use turpentine.
- -

32. Describing Acids and Bases

33. Chemical Properties of Acids
Tastes sour (if in food)
Reacts with metals
and carbonates
Turns blue litmus
paper red
pH < 7
Separate into H+ and
(-) ions in water

34. Never Taste a Chemical in a Lab
Acids in foods taste sour or tart: citrus fruits, tomatoes, apples, vinegar

35. Acids React with Metals & Carbonates
Acids corrode metals
H+ react with the metal
Chemical reaction producing H2 – gas
Acids react with carbonates to produce CO2

36. Strong Acid versus Weak Acid
A strong acid releases more H+ into solution. A weak acid only partially dissolves in water

37. Chemical Properties of Bases
Sodium Hydroxide - NaOH Potassium Hydroxide - KOH Ammonium Hydroxide - NH4OH Calcium Hydroxide - Ca(OH)2 Magnesium Hydroxide - Mg(OH)2 Barium Hydroxide - Ba(OH)2 Aluminum Hydroxide - Al(OH)3
Tastes bitter (if in food)
Feels slippery
Turns red litmus
paper blue
pH > 7
Causes OH- and
(+) ions in water

38. Bases in food taste bitter: radish, cabbage, Brussels sprouts, turnip, olives, coffee, unsweetened cocoa, quinine, Tums®

39. Indicator paper call tell
you if a substance is
acid (< 7), base (> 7)
or neutral (= 7)
The closer to 0, the
stronger the acid
The closer to 14, the
stronger the base (or
more alkaline)
The closer to 7, the
weaker the acid or base
Strength determines safety

40. What Happens If An Acid & Base Mix?
Neutralization = reaction between acid and base
Resulting substance is less acidic, less basic than the original substances
acid + base = a salt + water
How close to pH 7 depends on the concentrations and amounts of the originals