The Periodic Table (1.2) (M) Flashcards
What are the elements in the periodic table are arranged in order of? Why?
atomic (proton) number so that elements with similar properties are in columns, known as groups
What is in common between elements in the same group? What does this mean?
they have the same number of electrons in their outer shell (outer electrons) and this gives them similar chemical properties
In the periodic table, as you move down group 7, the boiling point increases. Why is this?
- the formula mass of atoms increase
- the intermolecular forces between the atoms become stronger
- more energy is needed to overcome these intermolecular forces
same for all non-elements (bar G8) as they often form diatomic molecules
Before the discovery of protons/neutrons/electrons, how did scientists attempt to classify elements?
by arranging them in order of their atomic weights
What is the problem with early periodic tables?
They were incomplete and some elements were placed in inappropriate groups (not matching properties) if the strict order of atomic weights was followed
How did Mendeleev overcome the problems with the early periodic table?
He left gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights
he only did 7 groups, leaving out the noble gases as they had not been discovered by 1869
2 points
Why was Mendeleev’s table considered accurate?
- Elements with properties predicted by Mendeleev were later discovered and filled the gaps.
- Knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct.
What ion do metals form?
positive
What are the elements tat do not form positive ions?
non-metals
The majority of elements are.. (metals or non-metals)
metals
Where are metals and non-metals found on the periodic table?
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.
3 factors
The electrostatic forces of attraction depend on which factors
- distance between outermost electrons and nucleus
- the number of occupied inner shells (energy levels) which provide a shielding effect
- the size of the positive charge on the nucleus (called the nuclear charge)
What the elements in Group 0 of the periodic table are called?
the noble gases
What are the chemical properties of the noble gases? Why?
They are unreactive and do not easily form molecules because their atoms have stable arrangements of electrons (full outer shell)
2 needed
What are the physical properties of noble gases?
- low boiling point
- low density
How many electrons do noble gases have in their outer shell? What is the exception?
The noble gases have eight electrons in their outer shell, except for helium, which has only two electrons.
How does the boiling point of noble gases correspond with their position in the group?
The boiling points of the noble gases increase with increasing relative atomic mass (going down the group)
Where are the noble gases placed in the periodic table?
to the right of Group 7
What are the elements in Group 1 of the periodic table are known as?
The alkali metals
Why do the alkali metals have characteristic properties? (number of electrons in outer shell)
because they have a single electron in their outer shell
3 needed
What are the physical properties of alkaline metals?
- are soft (they can be cut with a knife)
- have relatively low melting points
- have low densities
Why do the alkali metals have to be stored in oil?
To prevent them from reacting with oxygen in the air
What is formed when the alkaline metals react with water?
Metal hydroxide and hydrogen gas
What happens to the pH of water when an alkaline metal reacts with it?
rises above pH 7
If universal indicator is present, it will look blue or purple
Describe what you would observe when lithium, sodium and potassium react with water
Lithium: fizzes steadily; slowly becomes smaller until it disappears
Sodium: fizzes rapidly; melts to form a ball; quickly becomes smaller until it disappears
Potassium: burns violently with sparks and a lilac flame; quickly melts to form a ball; disappears rapidly, often with a small explosion
Describe the reaction of an alkaline metal and an oxygen
Metal oxide formed.
The alkali metals burn vigorously when heated and placed in a gas jar of oxygen. The oxide forms as white smoke
4 marks
Describe the reaction between an alkaline metal and chlorine gas
The group 1 elements react vigorously with chlorine. The products of the reactions are chlorides. At room temperature the chlorides are white solids. They dissolve in water to form colourless solutions.
2 needed
What are the physical properties of an ionic compound of an alkaline metal?
- white solid
- dissolve in water, giving a colourless solution
In Group 1, how does the boiling point of the elements correspond with their position in the group?
In Group 1, the boiling point of the elements decreases going down the group
Why do group 1 elements get more reactive going down the group?
- They have a larger atom going down the group
- Group 1 elements must lose an electron to obtain a full outer energy level
- Larger atoms lose electrons more easily
- Due to weaker electrostatic force of attraction (between electron lost and nucleus) because of:
- shielding effect from increased number of energy levels
- greater distance between nucleus and electron
- nuclear charge outweighed by these factors
why should hydrogen not be placed in Group 1/
It is a non-metal
What are the elements in Group 7 of the periodic table are known as?
The halogens
Why do the group 7 elements have similar reactions?
because they all have 7 electrons in their outer shell
3 things
In Group 7, the further down the group an element is, the higher its
relative molecular mass, melting point and boiling point
Are the halogens metals or non-metals?
non-metals
What do the molecules of halogens consist of?
a pair of atoms (diatomic molecules)
Describe the reaction between chlorine, bromine and iodine with a metal?
Chlorine: metal burns vigorously to produce orange-brown iron(III) chloride
Bromine: metal burns quickly to produce red-brown iron(III) bromide
Iodine: metal reacts slowly in iodine vapour to produce grey iron(II) iodide
Describe the reaction between chlorine, bromine and iodine with a non-metal?
Chlorine: explodes with a flame or in sunlight, forming hydrogen chloride
Bromine: vigorous reaction when warmed with hydrogen, forming hydrogen bromide
Iodine: very slow reaction when heated strongly, forming some hydrogen iodide
In Group 7, how does the reactivity of the elements correspond with their position in the group?
In Group 7, the reactivity of the elements decreases going down the group.
What are the physical properties of group 7 elements?
- low melting/boiling points
- poor conductors of heat and electricity
A more reactive halogen can (…) a less reactive halogen from an aqueous solution of its salt
displace
A halogen can only displace another in what? (state of matter)
an aqueous solution
Where are the transition metals in the periodic table?
In the central block
Why do Group 7’s boiling points increase as you move down the group?
Because as you move down the group, formula mass increases
so intermolecular forces increase in strength
so more energy needed to overcome these intermolecular forces
Why do Group 1’s melting/boiling points decrease as you move down the group?
As we go down group 1 the molecules increase in size (there are more energy levels)
So the metallic bonding decreases (is weaker) because the delocalised electrons are less attracted to the nucleus (weaker forces of attraction) as there is a greater distance between them
So take less energy to overcome/break these bonds
3 out of 5 needed
Describe some observations when sodium reacts with water
- effervescence / fizzing or bubbles or gas produced
- sodium melts or turns into a ball
- sodium moves (on the surface)
- steam / mist / vapour is produced
- sodium gets smaller / disappears
2 out of 3
Describe what you would see when sodium reacts with chlorine
flame
(white) solid forms
colour of gas/chlorine disappears/fades
