Atomic Structure And The Periodic Table Flashcards
What is a half equation?
Half equations show the separate process in terms of electron movement. One half equation shows the oxidation process, the loss of electrons, whilst the other shows the reduction process, which is the gain of electrons.
Example:
For 2Na + MgCl₂ —> 2NaCl + Mg:
2Na —> 2Na+ + 2e- (Sodium was oxidised)
Mg2+ + 2e- —> Mg (Magnesium was reduced)
What is an ionic equation
A balanced ionic equation shows the reacting ions in a chemical reaction.
Example:
AgNO₃(aq) + NaCl(aq) —> AgCl(s) + NaNO₃(aq)
An ionic equation can be used to show how just the AgCl(s) is formed.
Ag+(aq) + Cl-(aq) —> AgCl(s)
What is the difference between a compound and a mixture?
A compound is formed of two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed. Compounds can only be separated into elements by chemical reactions.
A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged. Mixtures can be separated by physical processes such as filtration, crystallisation, simple distillation, fractional distillation and chromatography.
Why did the new evidence from the scattering experiment lead to a change in the atomic model?
Most of the alpha particles that were scattered travelled straight through the atom, this led to the conclusion that most of the atom is empty space. A few alpha particles were reflected straight back by the dense positive nucleus. Hence, disproving the Plum Pudding model.
What is the difference between the plum pudding model and the nuclear model of the atom?
The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it. The nuclear model of the atom suggested that the mass was concentrated at the centre (nucleus) and that the nucleus was positively charged.
What are the relative charges of the subatomic particles?
Proton: +1
Neutron: 0
Electron: -1
How does the number of protons in the atom relate to the number of electrons and the type of element?
In an atom, the number of protons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge.
The number of protons in an atom of an element is its atomic number. All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of protons.
What is the radius of an atom and its nucleus?
The radius of an atom is about 0.1nm (1x10(-10)m)
The radius of the nucleus is less than 1/10000 of that of the atom ( about 1x10(-14)m)
What are the relative masses of the subatomic particles?
Proton: 1
Neutron: 1
Electron: very small
What is an isotope of an element?
An isotope of the same element must have the same number of protons but has a different number of neutrons.
What is the relative atomic mass of an element and how do you calculate it?
The relative atomic mass of an element is an average value that takes account of the abundance of the isotopes of the element.
Relative atomic mass = sum of: isotope mass x isotope abundance / 100
How are the electrons always arranged in an atom?
Electrons in an atom always occupy the lowest available energy level (innermost available shells). The electronic structure of an atom can be represented by numbers of by a diagram. For example, the electronic structure of sodium is 2,8,1.
What does an element’s position on the periodic table (group number, period number) tell us about the element?
The group number shows the number of electrons in the outermost shell (highest energy level) of the atom.
The period number tells us how many energy levels of electrons are in the atom.
What are the main steps in the development of the periodic table?
Before the discovery of protons, neutrons and electrons, scientists attempted to classify the elements by arranging them in order of their atomic weights.
The early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights was followed.
Mendeleev overcame some of the problems by leaving gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights.
Elements with properties predicted by Mendeleev were discovered and filled the gaps. Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct.
Where are metals and non-metals found on the periodic table and how do they react to form ions?
Elements that react to form positive ions are metals.
Elements that do not form positive ions are non-metals.
The majority of elements are metals. Metals are found to the left and towards the bottom of the periodic table. Non-metals are found towards the right and top of the periodic table.
What are the properties of Group 0 of the periodic table?
The elements in Group 0 of the periodic table are called the noble gases. They are unreactive and do not easily form molecules because their atoms have stable arrangements of electrons. The noble gases have eight electrons in their outer shell, except for helium, which has only two electrons.
The boiling points of the noble gases increase with increasing relative atomic mass (going down the group).
What are the properties of Group 1 of the periodic table?
The elements in Group 1 of the periodic table are known as the alkali metals and have characteristic properties because of the single electron in their outer shell.
Students should be able to describe the reactions of the first three alkali metals with oxygen, chlorine and water.
In Group 1, the reactivity of the elements increases going down the group.
What are the properties of Group 7 of the periodic table?
The elements in Group 7 of the periodic table are known as the halogens and have similar reactions because they all have seven electrons in their outer shell. The halogens are non-metals and consist of molecules made of pairs of atoms.
Students should be able to describe the nature of the compounds formed when chlorine, bromine and iodine react with metals and non-metals.
In Group 7, the further down the group an element is the higher its relative molecular mass, melting point and boiling point.
In Group 7, the reactivity of the elements decreases going down the group.
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.
