Atoms Physical Science BHHS 2010/Melmore

Learning Objectives Learning Objectives Apply an understanding of the structure of the atom. Be able to interpret numbers of subatomic particles making up each atom.

Atomic Models This model of the atom may look familiar to you. This is the Bohr model. In this model, the nucleus is orbited by electrons, which are in different energy levels. A model uses familiar ideas to explain unfamiliar facts observed in nature. A model can be changed as new information is collected.

ATOMIC STRUCTURE Particle Charge Mass proton + ve charge 1 neutron No charge 1 electron -ve charge nil

Atoms are the smallest particles of an element that retains the chemical properties of that element Parts: Nucleus – small region in the center of the atom. (+ charged protons, = charged neutrons) Electron Cloud – large region, compared to nucleus, where electrons are found.

Size of nucleus vs. electron cloud If an atom was the size of a sports stadium, the nucleus would be the size of a marble! Subatomic Particles: Protons : + charge, relative mass = 1.007 atomic mass units (amu); round to 1 Neutrons: = charge, relative mass = 1.009 atomic mass units (amu); round to 1 Electrons: - charge, relative mass = 0.0005 atomic mass units (amu); round to 0 (not factored in when figuring total mass of an atom)

Isotopes Atoms with the same number of protons & electrons but a different number of neutrons. They are the same element, but have different masses. All isotopes are used to calculate atomic mass (reason why weight is a decimal). Most elements consist of a mixture of isotopes.

Atomic Number Number of protons in the nucleus (also the number of electrons) Typically the number on top of the symbol on the Periodic Table. 13 Atomic Number 26.981

Mass Number Number of protons + number of neutrons in an atom. When solving for number of neutrons: round mass number properly, subtract atomic number from mass number.

Mass Number Mass number is the number of protons and neutrons in the nucleus of an isotope: Mass # = p+ + n0 Nuclide p+ n0 e- Mass # Oxygen - 10 - 33 42 - 31 15 18 8 8 18 Arsenic 75 33 75 Phosphorus 16 15 31

Complete Symbols Contain the symbol of the element, the mass number and the atomic number. X Superscript → Atomic number Subscript → Mass number

number of electrons = number of protons ATOMIC STRUCTURE He 2 Atomic number the number of protons in an atom 4 Atomic mass the number of protons and neutrons in an atom number of electrons = number of protons

Modern Atomic Structure electrons move so fast they look like a cloud and difficult to pinpoint

ATOMIC STRUCTURE Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. first shell a maximum of 2 electrons second shell a maximum of 8 electrons third shell a maximum of 8 electrons

Electrons are in energy levels Shells s p d f g Total 1 2 6 8 3 10 18 4 14 32

N DOT & CROSS DIAGRAMS Nitrogen With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example; X Nitrogen N 7 X X N X X 14 X X

ELECTRONIC CONFIGURATION With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example; Nitrogen configuration = 2 , 5 7 2 in 1st shell 5 in 2nd shell N 2 + 5 = 7 14

N DOT & CROSS DIAGRAMS Nitrogen With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example; X Nitrogen N 7 X X N X X 14 X X

DOT & CROSS DIAGRAMS O Cl Draw the Dot & Cross diagrams for the following elements; X 8 17 X O Cl a) b) X 35 X 16 X X X X X Cl X X X X X X X O X X X X X X X X X X

Pop QUIZ How many protons does Helium have How many electrons does Zinc have 3. Silver has ____electrons 4. Magnesium____electrons 5. Uranium____electrons 6. Kryption ______protons 7. Aluminium____electrons 8. Bromine ____mass 9. Calcium ____electrons 10. Sodium has ______protons

ATOMIC QUIZ 2: Written answers What is meant when an atom is said to be in its ground state? 3. The subatomic particle(s) found in the nucleus of an atom are 5. What is the maximum number of electrons that can occupy an atomic orbital? 8. In which way do isotopes of an element differ? 9. Calcium's atomic number is 20. What does that that tell us about a calcium atom? 10. What is ALWAYS true regarding atoms of two different elements?

Answers 1. What is meant when an atom is said to be in its ground state? CORRECT: The state an atom is found naturally. 3. The subatomic particle(s) found in the nucleus of an atom are CORRECT: protons and neutrons. 5. What is the maximum number of electrons that can occupy an atomic orbital? CORRECT: 2, 6, 10, 14 8. In which way do isotopes of an element differ? CORRECT: number of neutrons in the atom 9. Calcium's atomic number is 20. What does that that tell us about a calcium atom? CORRECT: It has 20 protons. 10. What is ALWAYS true regarding atoms of two different elements? CORRECT: They have different numbers of protons.

ELECTRONIC CONFIGURATION Write the electronic configuration for the following elements; 20 11 8 Na O Ca a) b) c) 16 23 40 2,8,8,2 2,8,1 2,6 17 14 5 Cl Si B d) e) f) 11 35 28 2,8,7 2,8,4 2,3

ELECTRONIC CONFIGURATION Write the name, electronic configuration and diagram for the following elements; 4 12 Ca 20 Be Mg 2) 3) 1) 40 8 24 2,8,2 2,8,8,2 2,2 6 14 32 Ge 4) C 5) Si 6) 72 12 28 2,4 2,8,4 2,8,18,4 31 5 Ga 13 B 7) 8) Al 9) 10 69 26 2,8,18,3 2,8,3 2,3 35 F 9 17 Br 10) 11) Cl 12) 18 79 34 2,7 2,8,7 2,8,18,7

DO YOU REMEMBER ? The Atomic Number of an atom is the............ The Atomic Mass of an atom is Protons in the nucleus equals the..... The number of Electrons = Electrons orbit the nucleus in _______ = number of protons in the nucleus. = number of Protons + Neutrons in the nucleus. = Number of Electrons. Number of Protons shells.

Structure of Subatomic Particles Subatomic particles composed of fast moving points of energy called quarks Quark Calculations (for protons and neutrons) Each proton is 2 up quarks and 1 down quark 2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1 Each neutron is 2 down quarks and 1 up quark 2(-1/3) + 2/3 = 0 Each electron is composed of 2 down quarks 3(-1/3) = -1