Unit 5: Atoms and Subatomic Particles Flashcards
Dalton’s Atomic Theory (3)
atoms are tiny particles that make up matter
atoms of an element are similar and different from other elements
in a chemical reaction atoms of two or more elements combine
Atomic Size
SMALLEST PARTICLE of an element that retains the PROPERTIES of that element
What are the three subatomic particles?
protons, electrons, neutrons
Like charges _____ and unlike charges _____
REPEL…..ATTRACT
What charge do protons have?
positive (+ve)
What charge does electrons have?
negative charge (-ve)
What charge do neutrons have?
neutral (0 charge)
Rutherford’s Gold-Foil experiment
+vely charged particles were aimed at atoms of gold
most went through the atoms
some were reflected occasionally
What was the theory at the time of Rutherford’s Gold-Foil Experiment?
charges (positive and negative) were distributed evenly throughout
the atom plum pudding model
Plum pudding model
the model that indicates charges within an atom as evenly distributed
not a lot of empty space in the atom
Who discovered electrons and when?
JJ Thompson in 1897
How did JJ Thompson discover electrons
passed an electric current through gas at low pressure, sealed in tubes with electrodes at either end
rays attracted to metal plates with a +ve charge and repelled by metal plates with a -ve charge.
he figured the ray was made up of -vely charged particles
electrons (e-)
Atoms are electrically….
neutral
What must equal what?
negative charge must = positive charge
Who discovered protons?
Goldstein in 1886
How did Goldstein discover protons
found rays traveling in opposite direction from cathode (Thompson’s) rays (e-)
What did Goldstein discover
particles that traveled in the opposite direction were protons
Organize the subatomic particles by weight lightest to heaviest
electron, proton, neutron
Who confirmed the existence of neutrons and when?
Chadwick in 1932
What did Chadwick discover?
confirmed the existence of neutrons
other info ab neutrons…
neutrons had no charge and a mass almost equal to mass of p+
Structure of an atom
nucleus that contains protons and neutrons
electrons are located in a large, empty space around the nucleus
Atomic Mass Unit (amu)
1/12 of the mass of the carbon-12 atom
What is the mass of a proton?
about 1 (1.007) amu
What subatomic particle has a mass of about 1 (1.007) amu?
proton
What is the mass of a neutron?
about 1 (1.008) amu
What subatomic particles has a mass of about 1 (1.008) amu?
neutron
What is the mass of an electron?
0.000549 amu
What subatomic particle has a mass of 0.000549 amu?
electron
What is found outside the nucleus?
electron
What is found inside the nucleus?
protons and neutrons
How are atoms different?
the number of protons is unique to each atom
Properties of Atomic Number (4)
specific for each element
same for all atoms of an element
equal to the protons in an atom
appears above the symbol of an element
If an atom of an element is electrically neutron…
the net charge of an atom is 0
When the net charge of an atom is 0…
the atom of the element is electrically neutron
An atom has an equal number of what?
protons and neutrons + electrons
idk what im saying
Mass Number
represents the number of particles in the nucleus
What is the mass number equal to?
number of protons + number of neutrons
If zinc has a mass number of 65 and an atomic number of 30 how many neutrons are in the zinc atom?
35
Isotope
atoms of the same element that have the same number of protons, but different numbers of neutrons
What does a nuclear symbol represent?
a particular ATOM of an element
Where is the atomic number and atomic mass located on a nuclear symbol?
Atomic Number: top left
Atomic Mass: bottom left
What is atomic mass the average of?
weighted average of masses for each individual isotope of an element
atomic mass
the mass of an atom (protons + neutrons)
atomic number
the number of protons in the nucleus
How are atoms of the same element alike?
same number of protons
Isotope average atomic mass calculation:
atomic mass = (mass 1 × %1) + (mass 2 × %2 ) +…and so on
Isotope average atomic mass calculation for PERCENTAGE/ABUNDANCE
atomic mass = (mass 1 × x) + (mass 2 × [1-x] )
What is a Bohr model?
a circle (nucleus) where protons and neutrons are located with rings around the nucleus where electrons are located
How does the Bohr model help us understand atoms?
helps us understand where the electrons lie within the atom
Who discovered that atoms were mostly empty space?
Rutherford
What were Rutherford’s conclusions to the Gold-Foil experiment?
atom is mostly empty space
there is a positive charge in the center (center is called the nucleus)
