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Day 1 atomic structure. Objective: SWBAT manipulate a virtual model of an atom in order to describe subatomic structure, net charge, atomic number and mass number distinguish between neutral, stable atoms, ions and isotopes construct 2D atomic models & nuclear symbols Warm-up :

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day 1 atomic structure
Day 1 atomic structure

Objective: SWBAT manipulate a virtual model of an atom in order to

  • describe subatomic structure, net charge, atomic number and mass number
  • distinguish between neutral, stable atoms, ions and isotopes
  • construct 2D atomic models & nuclear symbols

Warm-up:

  • Review: what are the defining features of an element?
  • Discuss at your table: How would you define an “atom”?
building an atom

Building An Atom

http://phet.colorado.edu/en/simulation/build-an-atom

day 2
Day 2

Objective: SWBAT manipulate a virtual model of an atom in order to

  • describe subatomic structure, net charge, atomic number and mass number
  • distinguish between neutral, stable atoms, ions and isotopes
  • construct 2D atomic models & nuclear symbols
slide9
Number of protons contained in an atom Determines the element

Every element of that kind has the same number of protons

Atomic Number

Mass Number

  • Number of protons and neutrons in an atom (p+ + n0)
  • Can change for various isotopes
mass number
Mass Number

Protons have a mass

Neutrons (although neutral) have a mass similar to protons

Electrons have a mass so small we don’t account for it in calculating the mass

Therefore the mass number is the sum of all protons and neutrons within the atom

Mass Number = P + N

When to use: When determining composition of a single atom! (this is not what’s on the PT)

atomic mass molar mass
Atomic Mass / Molar Mass

The atomic mass is a “weighted” average mass of all the stable isotopes of the element.

Finding Atomic Mass

For every stable isotope: Multiply the isotope’s mass number x % abundance (how often the element is found in that form) written as a decimal

After you do this for each stable isotope, add them all up

Av. Atomic Mass = Σ(Mass # x Abundance)

Not the Mass Number!!! – Atomic Mass is on the PT

This symbol means sum (add up all of these after you multiply)

slide12

Example: Carbon

    • Carbon – 12 (98.9% written as a decimal = .989)
    • Carbon – 13 (1.1% = .011)
    • Carbon – 14 (Not a stable isotope so not counted)
    • Av. Atomic Mass = (12 x .989) + (13 x .011) = 12.011
slide13
Differing number electrons (e-) changes overall charge of the atom

Cations (positive)

Anions (negative)

Ions

Isotopes

  • Differing number of neutrons (n0)
  • Changes Mass Number
ions anions cations
Ions – Anions/Cations

Anions (non-metals)

An atom with a net negative charge

More electrons than protons

Br- contains 35 protons, 36 electrons (-1)

Ca+ions (metals)

An atom with a net positive charge

More protons than electrons

Mg2+ contains 12 protons, 10 electrons (+2)

Remember: You NEVER change

the number of protons, just electrons

isotopes
Isotopes

An isotope is an element that contains a different number of neutrons.

Affects the molar mass of the element

Longhand notation

Element – Mass Number

Carbon – 12

Carbon – 14

Shorthand notation

Charge

Mass#

X

Atomic #

ionic charges

All elements want to become like the noble gases!

Alkali Metals – lose 1 e

Alkaline Earths – Lose 2 e

IIIA – Lose 3 e

IVA (carbon) – Lose 4 e / Gain 4 e

VA (Nitrogen) – Gain 3 e

VIA (oxygen) – Gain 2 e

Halogen – Gain 1 e

Noble Gases - neutral

Ionic Charges
electrons in an neutral atom
Electrons in an neutral atom

What must be true of (p+) and (e-) if an atom has neutral charge?

The atomic number is the number of protons (p+) in an atom

what do the numbers mean
What do the numbers mean?

Atomic Number

Atomic Symbol

Atomic Mass

On your table this may be different!

slide19
Fill in the following periodic table with the total number of electrons in a neutral species of the atom
valence electrons

e-

e-

e-

Valence Electrons
  • The number of electrons in the outer “shell” are known as valence electrons.
  • Use Bohr’s Model to picture this concept

First shell:

Second Shell:

Third shell:

2

8

Question: How many electrons fit in a shell?

18

slide21

Valence Electrons

1

2

The number of electrons in the outer shell of an atom

1

2

3

4

5

6

7

8

2

2

2

2

2

2

2

2

2

3

4

5

6

7

8

1

8

8

8

8

8

8

8

8

2

2

2

2

2

2

2

2