# Unit 3 – Nuclear Model of the atom

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Unit 3 – Nuclear Model of the atom
Atomic Composition Unit 3 – Nuclear Model of the atom

What do we know about atoms?
The atom is made of subatomic particles called nucleons. There are different types of nucleons

3 Major Subatomic Particles
ELECTRON e- Negatively Charged Atomic Mass – amu Basically round to zero amu

PROTON p+ Positive Charge Mass of amu Found in nucleus of atom

Neutron no No charge - “neutral” Mass of amu Found in Nucleus

Other Subatomic Particles

Computer Generated picture of two bombarded atoms.

Atomic Number Symbol -Z
ATOMIC NUMBER = NUMBER OF PROTONS All atoms of the same element have the same number of protons in the nucleus.

Mass Number Symbol -A Mass comes from the nucleus of the atom.
Mass number = # protons # neutrons

Number of neutrons = mass number minus atomic number
Neutral Atom -0r- Ground State No overall Charge Number of protons and electrons are the same Number of neutrons = mass number minus atomic number

Nitrogen ?protons, neutrons, electrons
Copper ?protons, neutrons, electrons PROTONS = 29 NEUTRONS= 35 ELECTRONS= 29 PROTONS = 7 NEUTRONS= 7 ELECTRONS= 7

What if it is not neutral?
Ion There was either: Gain of electron(s) Loss of electron(s) X- X+

Calculating nucleons in an ion
Example: How many protons, neutrons and electrons are there in Mg +2 In an atom or ion the number of protons is always the same. (atomic number) If an atom is not electrically neutral than there is an imbalance of the proton to electron ratio and we have an ion. If we have an ion one of two scenarios are present: Protons are in greater number than electrons so we have a positive ion. Protons are in less number than electrons so we have a negative ion.

Mg +2 ?proton neutrons electrons
Calculating the number of neutrons is the Mass number minus the atomic number Calculating electrons in an ion we have to look at the charge on the ion. If the ion is positive then there are more protons than electrons and if the number is negative then there are more electrons than protons Mg +2 ?proton neutrons electrons In an atom or ion the number of protons is always the same. (atomic number)

Mg +2 ?proton neutrons electrons
Magnesium has a mass number of 24 so the NEUTRONS = 24 (mass #) – 12(atomic #) = 12 Magnesium has a charge of a +2 so the number of protons are 2 more than the number of electrons. Since the number of protons does not change we will subtract 2 from the atomic number to give us ELECTRONS= 12 (atomic #) -2(the number on the charge = 10 the number of electrons. Mg +2 ?proton neutrons electrons Magnesium has an atomic number of 12 so the PROTONS = 12

Al+3 ?proton neutrons electrons
O-2 ?proton neutrons electrons PROTON = 8 NEUTRON = 16-8=8 ELECTRON = 8+2=10 PROTON = 13 NEUTRON = 27-13=14 ELECTRON = 13-3=10

Metals vs. Nonmetals METALS LOSE ELECTRONS BECOMING POSITIVELY CHARGED. NONMETALS GAIN ELECTRONS BECOMING NEGATIVELY CHARGED.

How do we write all of this information?
3. Add the # of neutrons to the number of protons. REMEMBER - this is the atomic mass. Complete Chemical Symbol Ni 59 4. Check to see if you have an atom or an ion. If the number or protons does not equal the number of electrons then you will need to add a + charge or a – charge. Write the symbol for the atom with 28 protons, 28 electrons and 31 neutrons. 28 1. Look up the symbol by using the number of protons. REMEMBER: the number of protons is the same as the atomic number. 2. Write the number of protons in the lower left hand side of the element.

How do we write all of this information?
3. Add the # of neutrons to the number of protons. REMEMBER - this is the atomic mass. Complete Chemical Symbol -2 O 16 4. Check to see if you have an atom or an ion. If the number or protons does not equal the number of electrons then you will need to add a + charge or a – charge. Write the symbol for the ion with 8 protons, 10 electrons and 8 neutrons. 8 1. Look up the symbol by using the number of protons. REMEMBER: the number of protons is the same as the atomic number. 2. Write the number of protons in the lower left hand side of the element.

How do we write all of this information?
3. Add the # of neutrons to the number of protons. REMEMBER - this is the atomic mass. Complete Chemical Symbol +2 Ca 40 4. Check to see if you have an atom or an ion. If the number or protons does not equal the number of electrons then you will need to add a + charge or a – charge. Write the symbol for the ion with 20 protons, 18 electrons and 20 neutrons. 20 1. Look up the symbol by using the number of protons. REMEMBER: the number of protons is the same as the atomic number. 2. Write the number of protons in the lower left hand side of the element.

How do we write all of this information?
Element name – atomic mass Protons – 73 1. The number of protons comes from the atomic number. How many protons, neutrons and electrons are in Tantalum-181. Electrons – 73 2. The number of electrons equals the number protons because this is a neutral atom. Neutrons – 108 3. The number of neutrons is equal to the mass number minus the atomic number.

Now it your turn to practice Complete the in class practice WS

Example Using the Bohr Model
1s22s22p63s1 1s22s22p63s23p5 Na is a metal and wants to lose an electron so it has a full energy level of electrons. Cl is a nonmetal and wants to gain and electron so it can have a full energy level.

Example Using the Bohr Model
1s22s22p6 1s22s22p63s23p6 11 protons and 10 electrons make an ion with a +1 charge. 17 protons and 18 electrons make an ion with a -1 charge.

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