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Atomic Structure
Atomic Structure
The modern model of the atom is based on the work of
A.) one scientist over a short period of time
B.) one scientist over a long period of time
C.) many scientists over a short period of time
D.) many scientists over a long period of time
In Rutherford's gold foil experiments, some alpha particles were deflected from their original paths but most passed through the foil with no deflection. Which statement about gold atoms is supported by these experimental observations?
A.) Gold atoms consist mostly of empty space
B.) Gold atoms are similar to alpha particles
C.) Alpha particles and gold nuclei have opposite charges
D.) Alpha particles are more dense than gold atoms
Atomic Structure
• Atoms have a small dense nucleus (contains most of the atoms mass)
• The nucleus is posi8vely charged and contains the protons and neutrons
Atomic Structure
• Electrons are clouded around the nucleus in regions called orbitals
• Most of the atom is empty space
Subatomic Par8cles
• Atoms contain subatomic par8cles called protons, neutrons, and electrons
Particle Location Charge Mass (amu)
Proton
Neutron
Electron
Nucleus +1 1
Nucleus 0 (neutral) 1
Outside Nucleus (orbital)
-1 1/1836 ~0
* Protons and neutrons are known collectively as nucleons *
The region labeled "X" in the diagram has a charge that is:
A.) positive
B.) negative
C.) neutral
The nucleus of most atoms is made up of:
A.) protons and electrons
B.) electrons and protons
C.) neutrons and electrons
D.) protons and neutrons
The _______________ constitute(s) most of the volume of an atom.
A.) nucleus
B.) protons
C.) electron cloud
D.) neutrons
The charge and mass number of a proton are:
A.) charge = 0, Mass number = 1
B.) charge = -1, Mass number = 0
C.) charge = +1, Mass number = 1
D.) charge = +1, Mass number = 0
The charge and mass number of an electron are:
A.) charge = -1, Mass number = 0
B.) charge = +1, Mass number = 0
C.) charge = 0, Mass number = 1
D.) charge = +1, Mass number = 1
The region labeled "Y" in the diagram has a charge that is:
A.) positive
B.) negative
C.) neutral
Most of the mass of the atom can be found in the:
A.) charges
B.) electron cloud
C.) electrons
D.) nucleus
In which pair do the particles have approximately the same mass?
A.) proton and electron
B.) proton and neutron
C.) neutron and electron
D.) neutron and beta particle
Which statement is true about the charges assigned to an electron and a proton?
A.) Both an electron and a proton are positive
B.) An electron is positive and a proton is negative
C.) An electron is negative and a proton is positive
D.) Both an electron and a proton are negative
The charge and mass number of a neutron are:
A.) charge = +1, Mass number = 0
B.) charge = 0, Mass number = 1
C.) charge = +1, Mass number = 1
D.) charge = -1, Mass number = 0
Elements
• Atoms of any given element always have the same number of protons
• Atomic Number = # of protons
Elements
• Ex: Carbons atomic number is 6 (all atoms of carbon have 6 protons)
• How many protons does Boron have?
• Which element has 19 protons? 5
Potassium
What is the total charge of the nucleus of a nitrogen atom?
A.) -7
B.) 0
C.) +7
D.) +14
What is the atomic number of an element that has six protons and eight neutrons?
A.) 2
B.) 6
C.) 8
D.) 14
Compared to a proton, an electron has
A.) a greater quantity of charge and the same sign
B.) a greater quantity of charge and the opposite sign
C.) the same quantity of charge and the same sign
D.) the same quantity of charge and the opposite sign
Charge of Atoms
• Atoms are electrically neutral • The number of electrons is equal to the number of protons in a neutral atom
• The nega8ve charge of the electron cancels the posi8ve charge of the proton
Charge of Atoms
• Ex: An atom of carbon has 6 electrons • How many electrons does an atom of Copper have? 29
What is the total number of electrons in an atom of potassium?
A.) 18
B.) 19
C.) 20
D.) 29
What is the total number of electrons found in an atom of sulfur?
A.) 6
B.) 8
C.) 16
D.) 32
Which two particles make up most of the mass of an atom?
A.) electron and neutron
B.) electron and proton
C.) proton and neutron
D.) proton and positron
Mass Number
• Sum of the number of protons and neutrons in an atom
• # of neutrons = mass number – atomic number
What is the mass number of an atom which contains 28 protons, 28 electrons, and 34 neutrons?
A.) 28
B.) 56
C.) 62
D.) 90
What is the total number of neutrons in an atom of an element that has a mass number of 19 and an atomic number of 9?
A.) 9
B.) 10
C.) 19
D.) 28
The mass number of an atom is determined by:
A.) adding the neutrons and electrons
B.) adding the protons and electrons
C.) the number of protons only
D.) adding the neutrons and protons
Fill in the Blanks
Atomic Symbol
Atomic Number
Protons Neutrons Electrons Mass Number
Na 12
40 50
78 195
10 9
Fe 56
11 11 11 23
Zr 40 40 90
Pt 78 117 78
F 9 9 19
26 26 30 26
Isotopes
• Atoms of an element (same number of protons) with a different number of neutrons
Carbon-12 Carbon-14
C 12
6 C14 6
Atomic Symbol
Mass Number
Atomic Number
6 neutrons 8 neutrons
The nucleus of an atom of cobalt-58 contains
A.) 27 protons and 31 neutrons
B.) 27 protons and 32 neutrons
C.) 59 protons and 60 neutrons
D.) 60 protons and 60 neutrons
The nucleus of which atom contains 48 neutrons?
A.) B.) C.) D.)
Atoms of different isotopes of the same element differ in their total number of
A.) protons
B.) neutrons
C.) electrons
Isotopes (such as hydrogen-1, hydrogen-2, and hydrogen-3) are atoms of the same element that differ in:
A.) the number of electrons
B.) the atomic number
C.) the number of protons in the nucleus
D.) the number of neutrons in the nucleus
E.) the mass number
Which atom contains exactly 15 protons?
A.) phosphorus-32
B.) sulfur-32
C.) oxygen-15
D.) nitrogen-15
Which atoms are isotopes of the same element?
A.) B.) C.) D.)
Atomic Mass
• A weighted average of all naturally occurring isotopes of an element
• Atomic Mass Unit (amu) – 1/12 the mass of a carbon-‐12 atom
Ques8on
• Copper has two isotopes: copper-‐63 and copper-‐65. The atomic mass of copper on the periodic table is 63.546 amu. Which of the isotopes is most abundant?
Copper-63
Ques8on
• A sample of copper is found to be composed of 72.5% Copper-‐63 and 27.5% Copper-‐65. What is the average atomic mass of Copper?
How to Determine Atomic Mass
1) Convert percent abundance to a decimal: divide by 100
Ex. Copper-‐63: 72.5% 72.5/100 = .725
Copper-‐65: 27.5% 27.5/100 = .275
How to Determine Atomic Mass
2) Find par8al masses of the isotopes: mul8ply the decimal by the mass
number of the isotope
Ex. Copper-‐63: .725 x 63 = 45.675
Copper-‐65: .275 x 65 = 17.875
Atomic Mass
3) Add up par8al masses to find the average atomic mass (answer must fall between lowest and highest isotope atomic mass!)
Ex. 45.675 + 17.875 = 63.55 amu
Example
• A sample of copper is found to be composed of 72.5% Copper-‐63 and 27.5% Copper-‐65. What is the average atomic mass of Copper?
• 72.5% Cu-‐63
• 27.5% Cu-‐65 0.725 0.275
x 63 x 65
= 45.675 = 17.875 +
63.55 amu
The atomic mass of an element is calculated using the
A.) atomic number and the ratios of its naturally occurring isotopes
B.) atomic number and the half-lives of each of its isotopes
C.) masses and the ratios of its naturally occurring isotopes
D.) masses and the half-lives of each of its isotopes
Atoms of an unknown element have the following masses and percent abundance: 90.92% of the atoms have a mass of 19.988 amu, 0.26% of the atoms have a mass of 20.983 amu and 8.82% of atoms have a mass of 21.978 amu. Calculate the average atomic mass of this element.
A.) 20.983 amu B.) 20.166 amu C.) 25.567 amu
D.) 19.988 amu
Ions
• An atom with a net charge (not neutral) • This is caused by having an unequal number of protons and electrons
• More electrons give a nega8ve charge, less electrons give a posi8ve charge
Na +1 Charge
The atomic number of an element is always equal to:
A.) the number of protons plus the number of neutrons
B.) the number of protons plus the number of electrons
C.) the number of neutrons in the atom
D.) the number of protons in the atom
E.) the number of electrons in the atom
When you change the number of electrons in an atom, you produce a different
A.) isotope
B.) type of atom
C.) ion
D.) mass number
Subatomic Summary:
• Protons = atomic number of element • Neutrons = mass number – protons
– If mass number is not given: use atomic mass from periodic table rounded to nearest whole number
Subatomic Summary:
• Electrons = equals number of protons* • * Ions (unequal protons and electrons)
– + means there are fewer electrons than protons (p>e)
– -‐ means there are more electrons than protons (e>p) • Do math to figure out charge!
Examples:
• Na+ – Protons: – Neutrons: – Electrons:
• S-‐2 – Protons: – Neutrons: – Electrons:
11
23 – 11 = 12
1 less electron = 10
16
32 – 16 = 16
2 more electrons = 18
Br-
P =
N =
E =
Krypton-81
P =
N =
E =
Ba+2
P =
N =
E =
How many electrons are contained in an Au+3 ion?
A.) 76
B.) 79
C.) 82
D.) 197
An ion with 5 protons, 6 neutrons, and a charge of +3 has an atomic number of
A.) 2
B.) 5
C.) 6
D.) 8
E.) 11
Fill in the Blank
Symbol Charge Mass Atomic # Protons Neutrons Electrons 32S -2
88 38 36
+1 24 10
-3 14 27
Sr +2 38 50
32 16 16 16 18
Na 11 11 13
Si 41 14 17
Atomic Objec8ves
• Basic atomic history • Rutherford’s Experiment and Conclusions
• Loca8on, Charge, and Mass of three subatomic par8cles
• Ions and Isotopes • Determining Average Atomic Mass
• Determine number of protons, nuetrons, and electrons for neutral atoms, ions, and isotopes
