Science Presentation Jesse and Dianna

ATOM MODEL

Model Of The Atom Atoms are composed of: Atoms are composed of: Positively Charged Protons Negatively Charged Electrons Neutrons with no charge Electrons are arranged in orbits Electrons are arranged in orbits called energy levels, or shells around the nucleus

Energy levels Energy levels are arranged based on their distance from the nucleus of the atom. Energy levels are arranged based on their distance from the nucleus of the atom. The first energy level can hold 2 electrons, the second can hold 8, and the third can also hold 8 The first energy level can hold 2 electrons, the second can hold 8, and the third can also hold 8 Valence electrons refer to the number of electrons that an atom’s outer most shell contains Valence electrons refer to the number of electrons that an atom’s outer most shell contains Atoms with the maximum amount of valence electrons in their outer most shell are more stable because they tend not to gain or lose electrons

Atom model Questions How many electrons can the 2 nd energy level hold within an atom? How many electrons can the 2 nd energy level hold within an atom? Which atom is more stable, Neon (with an atomic number of 10) or Magnesium (with an atomic number of 12)? Which atom is more stable, Neon (with an atomic number of 10) or Magnesium (with an atomic number of 12)? How many valence electrons does silicon (atomic number 14) have? How many valence electrons does silicon (atomic number 14) have?

Answers How many electrons can the 2 nd energy level hold within an atom? How many electrons can the 2 nd energy level hold within an atom? 8 Electrons 8 Electrons Which atom is more stable, Neon (with an atomic number of 10) or Magnesium (with an atomic number of 12)? Which atom is more stable, Neon (with an atomic number of 10) or Magnesium (with an atomic number of 12)? Neon, because it’s outer most shell of electrons is “full”. Neon, because it’s outer most shell of electrons is “full”. How many valence electrons does silicon (atomic number 14) have? How many valence electrons does silicon (atomic number 14) have? 4 valence electrons because the first two energy levels contain the first 10 electrons. 4 valence electrons because the first two energy levels contain the first 10 electrons.

PERIODIC TABLE

The periodic table is organized into periods and families.

iAiA 2A 3A4A5A6A7A8A9A10A11A12A 13A14A 15A 16A 17A 18A

Each box in the periodic table represents an element. 2A 3A4A5A6A7A8A9A10A11A12A 13A14A 15A 16A 17A 18A

Each box in the periodic table represents an element. ATOMIC SYMBOL

Each box in the periodic table represents an element. ATOMIC NUMBER

Each box in the periodic table represents an element. ATOMIC MASS NUMBER

Elements in the same period have the same number of energy levels. 2A 3A4A5A6A7A8A9A10A11A12A 13A14A 15A 16A 17A 18A

Elements in the same family have the same number of valence Electrons and similar properties. 2A 3A4A5A6A7A8A9A10A11A12A 13A14A 15A 16A 17A 18A

REVIEW QUESTIONS You should be looking at a periodic table for this. is a good one.

What element is in period 2 and group 13A?

BORON 2A 3A4A5A6A7A8A9A10A11A12A 13A14A 15A 16A 17A 18A

I am a halogen with 7 valence electrons and an atomic mass of about 127 amu. What am I? (Use ptable.com for this one.)

IODINE 2A 3A4A5A6A7A8A9A10A11A12A 13A14A 15A 16A 17A 18A

AVERAGE ATOMIC MASS

Elements have isotopes: forms of an element with different numbers of neutrons, but the same number of protons and electrons.

Isotopes of an element will be represented like this: 235 U Element Atomic Mass

FINDING AVG. ATOMIC MASS J 1 = atomic mass of isotope 1 J 2 = atomic mass of isotope 2 A 1 = abundance (%) of isotope 1 A 2 = abundance (%) of isotope 2 Avg. Atomic Mass = J 1 × A 1 + J 2 × A 2 Abundance = how often the isotope occurs in nature

REVIEW QUESTIONS

Rubidium has two common isotopes: 85 Rb (72.2%) and 87 Rb (27.8%). What is the average atomic mass of rubidium? (hint: use the formula)

J 1 = 85 amu J 2 = 87 amu A 1 = 72.2% A 2 = 27.8% Avg. Atomic Mass = 85 × × ≈ amu

Copper has two isotopes: 63Cu (69.09%) and 65Cu (30.91%). What is the average atomic mass of copper?

J 1 = 63 amu J 2 = 65 amu A 1 = 69.09% A 2 = 30.91% Avg. Atomic Mass = 63 × × ≈ amu

Why is the mass in amu of a carbon-12 atom reported as in the periodic table of the elements?

The masses on the periodic table are the average mass of all isotopes and their abundances found in the universe. Although carbon-12 weighs exactly 12 amu, the periodic table reports that the mass is because we are taking into consideration the abundances and masses of the other two carbon isotopes (carbon-13 and carbon-14)