Science- Atoms, radiation, waves
What is radiation?
The particles released from the nuclei of radioactive atoms.
What is radioactive decay?
The process of radioactive atoms releasing particles from their nuclei and changing into another type of atom.
What is an atom?
The basic building blocks of matter made out of protons, neutrons and electrons.
What is an electron?
a negatively charged subatomic particle.
what is a proton?
positively charged subatomic particle found in the nucleus.
what is a neutron?
A subatomic particle with a neutral charge in the nucleus.
What is a nucleus
The nucleus is the small, dense region consisting of protons and neutrons at the centre of an atom.
What does the atomic number represent?
The atomic number represents the number of protons in a nucleus.
What is the atomic number of this element?
6
What is the atomic number in this element?
Z
what does the mass number represent?
the total number of protons and neutrons together in an atomic nucleus.
what is the mass number of this element?
A
What is an element?
a pure substance that consists entirely of one type of atom.
What is a molecule?
When atoms combine with other atoms to form clusters they are known as molecules.
Molecule examples
H2O (water) and N2 (Nitrogen)
What is a compound?
two or more elements chemically combined and is made up of different types of atoms.
Compound examples
Salt (NaCl) and Carbon dioxide(CO2)
what is an ion?
an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons.
What is a positive ion?
If an atom loses an electron it will become POSITIVELY CHARGED. This ion is known as a cation.
Cation examples
Sodium atom (Na) loses an electron it becomes a POSITIVELY CHARGED. Na has a charge of +1 so written as (Na+)
Calcium (Ca) loses two electrons, becomes (Ca2+)
What is a negative ion?
If an atom gains an electron it will become NEGATIVELY CHARGED. This ion is known as an anion.
Anion examples
Chlorine (Cl) atom gains an electron it forms a NEGATIVE charge of -1. Symbol is (Cl-)
Oxygen gains two electrons. Symbol is (O2-)
What are isotopes?
Isotopes are atoms of the same element with different numbers of neutrons.
Isotope example.
carbon 12, which has 6 neutrons (plus 6 protons equals 12), carbon 13, which has 7 neutrons, and carbon 14, which has 8 neutrons.
Why are some isotypes unstable
They have too many protons or too many neutrons in the nucleus.
What is an alloy?
An alloy is a metal (known as the base metal) and is combined with small amounts of other elements
Alloy examples
Brass- alloy of copper and zinc
Gold- alloy of silver and copper (makes it stronger)
What are properties of metals?
- Solid at room temp (except Mercury Hg)
- Shiny if polished (Lustrous)
- Conduct electricity and heat
- Bend without breaking, squash and crush inti new shapes (malleable)
- can stretch into wires (ductile)
- Are dense, sink in water (Except Li, potassium K and sodium Na)
metal examples.
-Iron
-Aluminium
-Copper
-Gold
-Silver
(pure metals)
what are properties of non-metals?
-Solids, liquids and gases at room temperature
-Not shiny (dull)
-Do not conduct electricity or heat (except graphite, a form of Carbon C)
-Break easily if solid (brittle)
-Cannot stretch easily
-Relatively low melting and boiling points
non-metal examples
-Helium
-Oxygen
-Carbon (Graphite)
-Nitrogen
-Fluorine (drinking water)
What is a radioisotope?
Radioisotopes are radioactive isotopes of an element.
what is a radioisotope example?
uranium-235
What are the three types of radiation?
Alpha, beta, and gamma (released from unstable atoms)
Stable vs unstable nuclei
Most atoms that make up world are stable nuclei- nuclei will never undergo nuclear change.
Unstable nuclei can undergo nuclear decay at any moment- after, the atom will usually have a stable nucleus and wont decay further.
What is nuclear decay?
The nucleus does not sit still and the protons and neutrons are constantly moving and rearranging. These rearrangements can cause the nuclei to emit high-energy electromagnetic radiation and particles. This process is called nuclear decay, and is a type of nuclear reaction.
What can be achieved by a nuclear reaction?
To convert an atom into an atom of another element requires a change in the nucleus. This can only be achieved by nuclear reaction.
what are the symbols for alpha?
symbol for beta?
symbol for gamma?
what is alpha decay?
where a nucleus ejects an alpha particle, which is a cluster of 2 protons and 2 neutrons (same as helium)
what are alpha decay properties?
-relatively heavy particles so moves relatively slow (10% of the speed of light)
-occurs in atoms with very heavy nuclei where mass number is greater than 100
-sheet of paper could stop alpha particle
alpha decay example
uranium 238 undergoes alpha decay as it gives off alpha particles. Through this uranium atoms become thorium atoms.
What are beta decay properties?
- two different types: positive and negative
-particles are identical to electros and therefore very small
-negative beta has a negative charge (electrons)
-very light
-move at high speeds (90% of the speed of light)
- aluminium sheet could stop beta particles
What is negative beta decay?
Negative beta decay is when a nucleus undergoes beta decay, a neutron is converted into a proton and emits an electron. This increases the atomic number by 1 and a new element is formed, but the mass does not change.
what is positive beta decay?
Positive beta decay is when a nucleus undergoes beta decay, a proton is converted to a neutron and emits a positron. This decreases the atomic number by 1 and a new element is formed, the mass staying the same.
beta decay example
Carbon 14 (6 protons and 8 neutrons) turns into Nitrogen 14 (7 protons and 7 neutrons)
what is gamma decay?
Gamma decay is where protons and neutrons rearrange inside the nucleus but do not emit a particle. Instead, they emit a light.
what are Gamma Decay properties?
-travel at the speed of light
-like x-rays, but more powerful
-gamma rays can be stopped by hard concrete
what is a half-life?
half-life in an unstable isotope is the time it takes to lose half its mass.
what is the half-life from this graph?
5730 years (carbon 14)
What is a wave?
Wave motion is the transfer of energy without the transfer of matter.
What are the two types of waves?
Transverse and longitudinal.
What is a transverse wave?
In transverse waves, the oscillations are at right angles to the direction of travel and energy transfer.
What are transverse waves examples?
Light, types of electromagnetic radiation, water waves and S waves.
What are longitudinal waves?
In longitudinal waves, the oscillations are along the same direction as the direction of travel and energy transfer.
What are longitudinal wave examples?
Sound waves, waves in a stretched spring and P waves.
What are the properties of waves?
Frequency, amplitude, wavelength, speed and period.
What is frequency of a wave?
•the number of vibrations per second. Eg. 4 vibrations per second means the frequency is 4 Hertz (Hz). The frequency can be high or low. The higher the frequency the higher the energy of the wave.
What is amplitude?
•height of the wave. It is measured from the middle of the wave to the maximum distance from the middle position.
What is wavelength?
•the distance of one wave. Measured from one point on a wave to the same point on the next wave. Wavelength can be described as short or long
What is speed of a wave?
How quickly the wave travels. This can be described as fast or slow.
What is period?
•the time it takes for the wave to complete one cycle. This is measured in seconds.
label this wave:
What is the wave calculation formula?
v = f x λ
v = speed (m/s)
f = frequency (Hertz Hz)
λ = wavelength (metres m)
(remember triangle)
what is the electromagnetic spectrum?
The range of wavelengths or frequencies over which electromagnetic radiation extends.
-This categorises all the types of electromagnetic radiation on a spectrum.
-Electromagnetic radiation occurs due to the interaction between electricity and magnetism.
-The electromagnetic spectrum ranges from high frequency such as gamma radiation to low frequency such as radio waves.