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WRAP-UP��MDQ2 Why are atoms of elements different from one another? ��CH11-8 explore the properties and trends in the physical, structural and chemical aspects of matter

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Cornell note-taking

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http://slideplayer.com/slide/5719090/

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Elements

Elements are pure substances �(composed of one type of substance only). �They cannot be decomposed (broken apart) into other substances.�

There are 118 elements.�

The names of elements are written using symbols. These symbols are of 1 or 2 letters. �The first letter is written in uppercase; if there is a second letter, it is written in lowercase.�

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Elements

�Carbon is C

Cobalt is …

Copper is …

Calcium is …

Chlorine is …

Chromium is …

Cadmium is …

Caesium is …

Cerium is …

Curium is …

Californium is …

Copernicum is …

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Elements

�Carbon is C

Cobalt is Co

Copper is Cu

Calcium is Ca

Chlorine is Cl

Chromium is Cr

Cadmium is Cd

Caesium is Cs

Cerium is Ce

Curium is Cm

Californium is Cf

Copernicum is Cn

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Elements

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Elements are pure substances �(composed of one type of substance only). �They cannot be decomposed (broken apart) into other elements.�

Elements are composed (made up) of atoms. �

The atoms of one element are different from the atoms of other elements. �

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Elements

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�Copper atoms (Cu) are different from �silver atoms (Ag). �

Oxygen atoms are different from…

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ATOMIC

MODELS

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All atoms (except hydrogen) have 3 types of particles:

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Rules for Atoms

1. Atomic number: Z�

Atomic number = Z = number of protons in the nucleus of the atom = number of the element on the Periodic Table.�

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Rules for Atoms

��Any atom that has 3 protons is a lithium atom. ��All lithium atoms have 3 protons.

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Lithium is element number 3 on the Periodic Table.

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All uranium atoms have 92 protons, …

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Rules for Atoms

2. Mass number: A�

Mass number = A = number of protons + number of neutrons in the nucleus of the atom

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A = Z + N. �

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Rules for Atoms

3. Neutron number: N

Neutron number is found by rearranging the atomic mass equation A = Z + N to become: � N = A - Z �

N is calculated for a single atom. �

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Rules for Atoms

3. Neutron number: N�

Neutron number = N = is calculated for a single atom = found by rearranging the atomic mass equation A = Z + N to become: � � N = A - Z �

The number of neutrons in the atoms of the same element can vary. Atoms of the same element that have different numbers of neutrons are called isotopes of each other.�

Cl-35 and Cl-37 are isotopes of chlorine.

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Rules for Atoms

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Calculate the average atomic mass of chlorine, where Cl-35 is 75.5% and Cl-37 is 24.5%.

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What is the value shown on the Periodic Table?

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Rules for Atoms

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Rules for Atoms

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Rules for Atoms

4. Electron number

The number of electrons equals the number of protons in a neutral (uncharged) atom. �

A carbon atom has 6 protons, therefore the neutral carbon atom has 6 electrons. �

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Rules for Atoms

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Neptunium atoms have … electrons

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Americium atoms have … electrons

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Rules for Atoms

5. Electron position�

Electrons

  1. move so fast that they cannot be located with any certainty
  2. are described as forming a probability cloud (within which they may be found) of negative charge around the nucleus
  3. contain only around 1/2000 the mass of a proton or neutron, but occupy around 90% of the volume of the atom�

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Rules for Atoms

5. Electron arrangement�

  1. Electrons are arranged in energy levels (orbitals) around the nucleus
  2. Only two electrons can occupy a single orbital
  3. Electrons fill the orbitals of lowest energy (closer to the nucleus) before filling those of higher energy (further away from the nucleus). �

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Simple explanation video:

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https://www.youtube.com/watch?v=lqWL0WMtlYk�

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More complex (much more than you need, just if you are interested)

https://www.youtube.com/watch?v=CP35NuspGlk

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Keep this – awesome PT

http://www.ptable.com/

Method 2

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https://www.youtube.com/watch?v=hJ0WwAGSjlc

Rules for Atoms

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Rules for Atoms

5. Electron arrangement�

  1. Fill orbitals in the order:

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 �5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6 8s2 5g18 6f14 7d10 8p6 9s2�

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Rules for Atoms

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Rules for Atoms

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When Atoms Change

The nuclei of atoms can be unstable and can emit particles (alpha-, beta-,…- emission) and energy (gamma radiation).

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When Atoms Change

Neutron-proton ratio too high

Neutron-proton ratio too low

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When Atoms Change

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  • For which nuclear condition is alpha-decay a solution?��A) too many neutrons�B) too many protons�C) nucleus too big�D) too much energy in the nucleus��Alpha decay typically occurs in the heaviest nuclides, where p:n ratio > 1.5 : 1

When Atoms Change

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When Atoms Change

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  • For which nuclear condition is beta-decay a solution?��A) too many neutrons�B) too many protons�C) nucleus too big�D) too much energy in the nucleus

When Atoms Change

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When Atoms Change

Radioactive isotopes are used in industry and in medicine.�

Identify one of each.