Properties of atoms and Radioactivity + History Flashcards
Define atoms and provide insight into their structure.
Atoms are the smallest unit of matter where all matter is made up of atoms. The atomic structure consists of 3 subatomic particles; the neutrons and protons ( collectively called nucleons ) which make up the nucleus at the center of the atom and the electrons which surround it in shells of various energy levels.
What holds together the nucleus?
The Strong Nuclear Force holds together the nucleus.
Define Atomic Number, Atomic Mass and Mass Number.
Atomic number : The number of protons in an atom. ( This also tells of the number of electrons as atoms are neutral in charge. )
Atomic Mass: The atomic mass is the average mass number of all of the isotopes of a particular element in ratio to their abundance within the natural world.
Mass number : As electrons are essentially weightless, the mass number denotes only the number of protons and neutrons.
What are the 2 classifications of matter? Describe them.
Matter can be classified as pure substances or mixtures. Pure substances further classify as elements or compounds.
Elements are substances which contain ONLY ONE type of atom.
Compounds are substances which contain two or more types of atoms which are CHEMICALLY BONDED.
Mixtures are made up of 2 or more pure substances which are NOT bonded chemically.
How many groups and periods are in the periodic table, how does this effect the properties of atoms?
There are 7 periods and 18 groups ( 8 GROUPS WITH 10 GROUPS OF TRANSITION METALS IN BETWEEN ) in the periodic table. Elements of the same period have the same number of electron shells whereas elements of the same group have the same number of electrons in their valence shell.
What are some properties of lanthanides and actinides?
Both are metals and are similar in reactivity to the Group 2 alkaline earth metals. Actinides are generally all radioactive whereas Lanthanides are not.
How does the periodic table assist in determining whether a substance is metallic?
Apart from hydrogen, metals are towards the left of the periodic table whereas nonmetals are towards the right.
Starting from boron ( group 13 ) and staircasing down are the nonmetals.
Use the periodic table to determine the charge of ions.
For the most part, Elements in :
Group 1 lose 1 electron
Group 2 lose 2 electrons
Group 3 lose 3 electrons
Group 4 lose or gain 4 electrons
Group 5 gain 3 electrons
Group 6 gain 2 electrons
Group 7 gain 1 electrons
Group 8 does not react.
However, beyond groups 1 and 2, elements tend to be able to form more than one ion, hence some metals such as Iron have to be written as Fe ( II ) for a charge of 2+ and Fe ( III) has a charge of 3+.
Why are noble gases so unreactive?
Noble gases have eight electrons in their outermost shell, except in the case of helium, which has two.
What does Rutherford’s gold foil experiment show?
Upon directing alpha particles at a thin piece of gold foil, most of the positively charged alpha particles went right through. This showed that :
- Atoms were mostly empty space. When the alpha particles hit the nucleus of the gold atoms, it would deflect off due to the repulsion of like forces. However, only a small amount of alpha particles were deflected, meaning that the nucleus only took up a tiny portion of the atomic radius.
In what order were the subatomic particles discovered and by who were they discovered?
The first subatomic particle to be discovered was the ELECTRON, identified in 1897 by J. J. THOMSON
After the nucleus of the atom was discovered in 1911 by Ernest RUTHERFORD, the nucleus of ordinary hydrogen was recognized to be a single PROTON
Last, James Chadwick discovered neutrons in the year 1932
Alpha particles properties?
Alpha radiationis essentially the emission of ahelium nucleus. Change in :
Charge : -2 change
Mass number : -4 change
Alpha particles are heavy and hence slow to deflect highly ionizing.
Beta particles properties? ( what are the 2 types? )
β−decay is the emission of anegatively charged electron. This is modelled by aneutronchanging into aproton and anelectron.
Charge: +1 change
Mass : 0 change
β+decay is the emission of apositively charged electron. This is modelled by aproton changing into aneutronand an positron.
Charge: -1 change
Mass : 0 change
Beta particles are easy to deflect as they are light.
Gamma rays properties?
Gamma radiationis a form of veryhigh frequencyelectromagnetic radiation. They can be described as photons (massless particles) which travel as waves at the speed of light.
Charge: 0 change
Mass : 0 change
What are isotopes ?
Isotopes are variations of elements in which the number of neutrons are different but the number of protons and electrons remain the same and balanced.
