Summative Assessment Review! Ms. Barlow’s HS PS Class

Phase Particle Properties ProximityEnergyMotionVolumeShape Solid Liquid Gas close littlevibrationaldefinite closemoderaterotationaldefiniteindefinite far aparta lottranslationalindefinite

Phase Change Diagram

Gas Laws Boyle determined that for the same amount of a gas at constant temperature, results in an inverse relationship: when one goes up, the other comes down.

Charles’ Law As the volume increases the temperature also increases. If the temperature decreases than the volume also decreases.

ATOMIC NUMBER: the number of protons in the nucleus of an atom. Atomic Mass – Atomic Number = Number of Neutrons Number of Protons = Number of Electrons

Valence Electrons Farthest away from the nucleus and are involved in bonding Electron Dot Diagram: Way to show the # of valence electrons. Gain or loss of electrons is called ionization lose an electron; atom becomes positive gain an electron; atom becomes negative Farthest away from the nucleus and are involved in bonding Electron Dot Diagram: Way to show the # of valence electrons. Gain or loss of electrons is called ionization lose an electron; atom becomes positive gain an electron; atom becomes negative

Isotopes Atoms with the same number of protons but a different number of neutrons. Example: an atom with one proton, one electron and one neutron is hydrogen. However, if the hydrogen atoms has two particles (neutrons) but the same number of protons (in the case of hydrogen one) it is an isotope of hydrogen.

Radioactivity Radioactivity is the breaking down of atomic nuclei by releasing particles (primarily alpha and beta particles) or electromagnetic radiation (primarily gamma rays).

Alpha Particles Alpha particles are positively charges particles. Alpha particles consists of two protons and two neutrons. An alpha particle is simply a helium nuclei (He) which is ejected with high energy from an unstable nucleus Alpha particles are positively charges particles. Alpha particles consists of two protons and two neutrons. An alpha particle is simply a helium nuclei (He) which is ejected with high energy from an unstable nucleus

When an atom loses an alpha particle, the Z number (atomic number) is lower by two, so move back two spaces on the periodic table to find what the new element is. The new element has an A number (atomic mass number) that is four less than the original elements.

Example

Beta Particles Beta particles are electrons. They are negatively charged (-1). They are fast moving because they are actually electrons. It is produce when a neutron in the nucleus breaks up into a proton and an electron. The proton remains inside the nucleus, increasing its atomic number by one but the electron is given off. Beta particles are electrons. They are negatively charged (-1). They are fast moving because they are actually electrons. It is produce when a neutron in the nucleus breaks up into a proton and an electron. The proton remains inside the nucleus, increasing its atomic number by one but the electron is given off.

Example – Carbon -14 They are written as an electron (along with a proton) which is emitted from the nucleus as a neutron decays.

The Z number (atomic number) actually adds one since its total must be the same on both the left and the right of the arrow and the electron on the right adds a negative one. The A (atomic mass)number is unchanged. The Z number determines the element so look for it on the Periodic Table. The Z number (atomic number) actually adds one since its total must be the same on both the left and the right of the arrow and the electron on the right adds a negative one. The A (atomic mass)number is unchanged. The Z number determines the element so look for it on the Periodic Table.

Gamma Rays Gamma rays are electromagnetic waves with extremely short wavelengths. They have no mass or charge so the Z and A numbers are not affected. They travel at the speed of light. It takes a thick block of lead to stop them. Radioactive atoms often emit gamma rays along with either alpha or beta particles. Gamma rays are electromagnetic waves with extremely short wavelengths. They have no mass or charge so the Z and A numbers are not affected. They travel at the speed of light. It takes a thick block of lead to stop them. Radioactive atoms often emit gamma rays along with either alpha or beta particles.

Examples

NameAlphaBetaGamma Greek letter --  Symbol Composition 2p +, 2n 0 electronEM wave Charge2+1-0 Stopped by paper, skin, clothing wood, glass thick concrete or lead

a. alpha emission b. beta emission c. electron capture ______________ _______________

Standard: Explain the process of half- life as related to radioactive decay. Radioactive Decay During radioactive decay an unstable nucleus spontaneously decomposes to form a different nucleus, giving off radiation in the form of atomic particles or high energy rays. This decay occurs at a constant, predictable rate that is referred to as half-life. A stable nucleus will not undergo this kind of decay and is thus non-radioactive. Radioactive Decay During radioactive decay an unstable nucleus spontaneously decomposes to form a different nucleus, giving off radiation in the form of atomic particles or high energy rays. This decay occurs at a constant, predictable rate that is referred to as half-life. A stable nucleus will not undergo this kind of decay and is thus non-radioactive.

Calculating Half-Life Solve the following problem: If 20 mg of iodine 31 is given to a patient, how much is left after 32 days? The half-life of iodine-131 is 8 days. Here's what you do:

Here's what you do: Find how many times the substance will be halved in 32 days. Do this by seeing how many times 8, the half- life of the substance, can go into 32, the amount of days. 32/8 = 4, so the amount of substance is halved four times. This means that after 8 days, you will have 20mg/2, or 10 mg of substance; after 16 days, you will have 10 mg/2 or 4 mg left of the substance; after 24 days, you will have 5 mg/2, or 2.5 mg left of the substance, and after 32 days, you will have 2.5 mg/2, or 1.25 mg left of the substance. Find how many times the substance will be halved in 32 days. Do this by seeing how many times 8, the half- life of the substance, can go into 32, the amount of days. 32/8 = 4, so the amount of substance is halved four times. This means that after 8 days, you will have 20mg/2, or 10 mg of substance; after 16 days, you will have 10 mg/2 or 4 mg left of the substance; after 24 days, you will have 5 mg/2, or 2.5 mg left of the substance, and after 32 days, you will have 2.5 mg/2, or 1.25 mg left of the substance.

Solve the following problem: If a laboratory receives a shipment of 200 g of technetium- 99m and only 12.5 of the isotope remains, what is the half-life of technetium-99m?

Here’s what you do: Work backwards. If 12.5g of the substance remains, then before it was halved, there was 25 g of the substance (12.5 x 2); before that, there was 50 g of the substance; before that, you had 100g, and before that, you had 200g. This means that the substance had to be halved 4 times to get from 200 g to 12.5 g, which means that the half life is 24 hours/4 times, or 6 hours.

Solve the following problem: If the half-life of uranium-232 is 70 years, how many half-lives will it take for 20g of it to be reduced to 1.25g?

Here’s what you do: Start with 20g and start reducing. 20g/2 = 10g (1 half life), 10g/2 = 5 (2 half lives), 5g/2 = 2.5 (3 half lives), and 2.5/2 = 1.25 (4 half lives). The answer is 4 half lives.

Nuclear Fission The splitting of a nucleus into smaller fragments is called nuclear fission. Heavy atoms (mass number>60) tend to break into smaller atoms, thereby increasing their stability. Nuclear fission releases a large amount of energy.

Nuclear Fission

A chain reaction can only occur if the starting material has enough mass to sustain a chain reaction. This amount is called the critical mass. Nuclear Fission is what occurs in Nuclear Reactors and Atomic Bombs. The Nuclear reactor is a controlled fission reaction, the bomb is not.

Nuclear Fusion The combining of atomic nuclei to form a larger atom is called fusion Nuclear fusion occurs in the sun where hydrogen atoms fuse to form helium 4 H e -  He + energy

Nuclear Fusion

Fusion Fusion reactions also release very large amount of energy but require extremely high temperatures to start. Nuclear fusion also occurs in new stars and is how all of our elements were made. He + He  Be + energy He + Be  C + energy

Decay vs. Nuclear Reactions Alpha, beta, and gamma decay occur as ONE atom tries to increase it’s stability by getting rid of a few neutrons, or protons & neutrons. The product is an alpha, beta, or gamma particle and ONE new atom. There is only ONE thing on the left hand side. Nuclear reactions involve more than just getting rid of a few protons or neutrons. The new atoms produced are VERY different elements than the reactant. Nuclear reactions must be started, so there are 2 things on the left hand side. – Nuclear fission: makes 2 or more much smaller atoms – Nuclear fusion: makes 1 much larger atom