1. Atoms and Their Interactions Chapter 6.1

2. I. Element – a substance that cannot be further
I. Element – a substance that cannot be further broken down and still retain an identity. Everything is made of elements.

3. Atom – smallest part of an element, cannot be broken down in ordinary chemical reactions.
1. Made up of:
a. Protons = + charge
b. Electrons = - charge
c. Neutrons = no charge
d. Nucleus = P + N
2. Atomic Number = number of protons in the nucleus.
3. Atomic Mass = number of protons + neutrons.
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4. a. Electrons orbit the nucleus in orbits (paths).
4. Electrons – always the same number of electrons as protons in an atom (atoms have no net charge).
a. Electrons orbit the nucleus in orbits (paths).
b. Orbits form Energy Levels around the nucleus.
1. First energy level has one orbit or maximum of 2 electrons.
2. Second energy level has four orbits, or maximum of 8 electrons.
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5. Isotopes – Atoms of the same element with different numbers of neutrons and therefore, different atomic masses.
Radioactive Isotopes – nuclei break down and give off radiation – useful in treating cancer.
Ions – charged atoms.
Do not have the same number of protons and electrons.
Have a NET positive or negative charge.
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6. Compounds – chemical combinations of elements.
A. Molecule – smallest part of a compound.
B. Bonding – process of atoms being chemically linked together to form molecules. Requires ENERGY or a BOND.
C. Types of Bonds
1. Covalent – electrons are shared between atoms.
2. Ionic – electrons are transferred between atoms.
D. Chemical Bonding – atoms react chemically until they are stable (energy levels are full of electrons).
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7. Chemical Symbols and Chemical Formulae
A. Every element has a shorthand form or symbol – of one or two letters.
B. Chemical Formulae
1. Molecules have definite proportions of elements.
2. Subscripts – indicate how many ATOMS of the preceding element.
3. Whole numbers in front of the formula indicate how many molecules of the substance. These are called Coefficients.
4. Examples:
a. H2O
b. 6C6H12O6
c. NH3

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9. Mixtures – no chemical change or bonding of atoms.
A. Association of substances is physical.
B. Substances may be separated by physical means.
C. Proportions are variable.
D. Mixture has properties of the various substances forming it.
E. Solution – mixture in which one or more substances are distributed evenly in another substance.
1. Solvent – dissolving material
2. Solute – material dissolved
3. Examples: sugar water, tea, coffee.
The coffee is the solvent, the sugar is the solute, and the sweeten coffee would be the solution. 

10. Acids and Bases A. Acid – sour taste
1. Release hydrogen ions (H+) in solution.
2. pH of less than 7.
B. Bases – bitter taste
1. Release hydroxide (OH-) in solution.
2. pH more than 7.
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12. Citations
The pH Scale. United Learning unitedstreaming. 16 September
Atomic Number, Mass Number, Isotopes. United Learning unitedstreaming. 27 September
Isotopes. United Learning unitedstreaming. 27 September