Nuclear Reactions

Subatomic Particles The atoms of each element behave very differently, but they all have something very important in common. Every atom is made of the same subatomic particles.

1 1 Understanding the mass of atoms: When discussing subatomic particles, scientists often talk about their relative masses. This just means how their masses compare to one another. Protons Neutrons Electrons Relative Mass 1 1 1 1840

Understanding the mass of atoms: Because electrons are 1/1840th the size of protons and neutrons, they are too small to concern ourselves with when we are discussing mass. Electrons 1 1840

What is the identity of each of the elements below. Hydrogen Lithium Helium Elements are identified by the number of protons in the nuclei of the atoms that make up the element. Atoms of the same element can have different numbers of neutrons. Atoms of the same element with different numbers of neutrons are called isotopes.

Atoms get their mass numbers from their relative mass. Hydrogen-2 Lithium-7 Helium-4 The mass number is the total number of protons and neutrons in the nucleus. We identify different isotopes by noting their mass numbers.

How many neutrons are in the nucleus of a helium-5 atom? Mass numbers do NOT tell us the number of neutrons in an isotope. To find the number of neutrons in an isotope, you must take the mass number and subtract the atomic number # of neutrons = mass number – atomic number How many neutrons are in the nucleus of a helium-5 atom? Helium-5 5 – 2 = 3 neutrons

What would the mass number be? Knowing the number of protons and neutrons allows you to identify an isotope. Identify the Isotope with this combination of protons and neutrons. 4 protons and 5 neutrons = ____________ Beryllium - 9 Which element would have 4 protons? Beryllium What would the mass number be? 4 + 5 = 9

C 13 6 Understanding Isotopes As we discuss nuclear chemistry, we will be using a special notation for specific isotopes. As usual, we will use an element’s symbol to abbreviate the element. C 13 To identify the specific isotope, we will place the mass number in the top left corner next to the symbol. 6 It will be necessary to know the atomic number as well. This is placed on the bottom left.

C U N Understanding Isotopes 13 235 14 6 92 7 Most of the time, the atomic numbers will not be written for you before you begin. These will have to the added by you. What atomic numbers should be added to the chemical symbols below. C U N 13 235 14 6 92 7

Add the correct atomic numbers to each of the isotopes on your notes.

Unstable Isotopes There are several different isotopes for any given element. Some of these isotopes will be stable, while other will be unstable. C 12 6 C 13 6 C 14 6 Stable Stable Unstable Unstable isotopes eventually undergo the process of nuclear decay. This means that the atoms break apart releasing energy and particles.

He Types of Nuclear Decay 4 2 The largest particle that is emitted from a nucleus during nuclear decay is known as an alpha (α) particle. Alpha particles are composed of 2 protons and 2 neutrons. These means that they have a mass number of 4 He and an atomic number of 2. 4 Because it has 2 protons and 2 neutrons, this is essentially the nucleus of a helium atom. 2

They have a -1 charge, so we place this in the atomic number spot. Types of Nuclear Decay Very tiny negatively charged particles can also be emitted during nuclear decay. These are known as beta (β) particles. Beta particles are essentially electrons that are emitted from the nucleus of an atom. Remember, electrons do not have enough mass to consider, so we place a 0 in the mass number spot. e They have a -1 charge, so we place this in the atomic number spot. -1 Because beta particles are essentially electrons, we use the letter e as a symbol.

N C Beta Decay 14 7 6 Nitrogen-14 Carbon-14 When a nucleus undergoes beta decay, an electron is emitted from a neutron. When the negative charge leaves the neutron, the neutron becomes a proton! This causes the mass to remain constant, but the atomic number increases by one. N C 14 7 6 Nitrogen-14 Carbon-14

They have a +1 charge, so we place this in the atomic number spot. Types of Nuclear Decay Another very tiny particle that can be emitted during nuclear decay is known as a positron. Positrons are very similar to electrons in size, but they have a +1 charge. Just like electrons , positrons do not have enough mass to consider, so we place a 0 in the mass number spot. e They have a +1 charge, so we place this in the atomic number spot. +1 Because positrons are the antiparticles of electrons, we still use the letter e as a symbol.

B C Unstable Isotopes 11 5 6 Boron-11 Carbon-11 When a nucleus undergoes a positron emission, a positron is emitted from a proton. When the positive charge leaves the proton, the proton becomes a neutron. This causes the mass to remain constant, but the atomic number decreases by one. B C 11 5 6 Boron-11 Carbon-11

Gamma (γ) radiation Whenever a nuclear reaction occurs, there is a large amount of energy released. This energy includes all types of radiation including the highest energy radiation known as gamma (γ) rays. Gamma rays are energy and not matter, but they could appear in a nuclear reaction equation. γ They have no mass, so we a 0 in the mass number spot. They have no charge, so we a 0 in the atomic number spot.

n Types of Nuclear Decay 1 Neutrons are also often involved in nuclear reactions. They can be shot into a nucleus to trigger a nuclear reaction or emitted from the nucleus after a nuclear reaction. Just like protons, neutrons have a mass of 1. n 1 They have no charge, so we a 0 in the atomic number spot. We use a lowercase n as the symbol for a neutron. This is to keep it from being confused with nitrogen.

Balancing Nuclear Reactions Nuclear reactions are very easy to balance. Once again, we think of the arrow as our equal sign. Then, we follow a few easy steps. 239Pu  4He + 94 2 Step 1: Write atomic numbers for the elements if they are not already there.

Balancing Nuclear Reactions Nuclear reactions are very easy to balance. Once again, we think of the arrow as our equal sign. Then, we follow a few easy steps. 239Pu  4He + 235 92 94 2 Step 2: Use simple algebra to determine the mass number and atomic number of the unknown element.

Balancing Nuclear Reactions Nuclear reactions are very easy to balance. Once again, we think of the arrow as our equal sign. Then, we follow a few easy steps. 239Pu  4He + U 235 92 94 2 Step 3: Use the atomic number to determine which element’s symbol should be placed in the blank.

Complete the nuclear reaction problems on your notes.

Types of Nuclear Reactions There are 2 main types of nuclear reactions you need to be familiar with: fission and fusion. Fission reactions occur when a nucleus breaks apart into several smaller nuclei. The first atom bombs were the result of a fission reaction.

Types of Nuclear Reactions There are 2 main types of nuclear reactions you need to be familiar with: fission and fusion. Fusion reactions occur when a nuclei join together into one larger nucleus. Fusion reactions are what occur in the sun and other stars. Image from Wikipedia

The high energy radiation released during nuclear reactions can lead to radiation poisoning which can cause serious illnesses and commonly leads to death. Because of this, radioactive substances must be treated with great care. Radioactive Substance