The Periodic Table Flashcards
All 36 cards in this deck
In what order are the elements arranged in the modern periodic table?
In order of atomic (proton) number.
Why is the periodic table called 'periodic'?
Because elements with similar properties occur at regular intervals.
What do all elements in the same group of the periodic table have in common?
The same number of electrons in their outer shell, which gives them similar chemical properties.
What does the period (row) number of an element tell you about its atoms?
e.g. an element in Period 3
The number of occupied electron shells (energy levels).
e.g. a Period 3 element has 3 shells.
True or false? Elements in the same period (row) have similar chemical properties.
False. Elements in the same group (column) have similar chemical properties, because they have the same number of outer electrons.
Before protons, neutrons and electrons were discovered, how did scientists try to classify the elements?
By arranging them in order of their atomic weights.
What two things did Mendeleev do to overcome the problems with earlier periodic tables?
He left gaps for elements not yet discovered, and in some places changed the order based on atomic weights.
Why did Mendeleev reverse the order of some pairs of elements?
So that their properties matched the rest of the group.
True or false? Mendeleev swapped some pairs of elements so that they were in order of atomic number.
False. Atomic number is the number of protons, and protons had not been discovered yet — he swapped them so properties matched the group.
What discovery explained why ordering elements by atomic weight was not always correct?
The discovery of isotopes — atoms of the same element can have different masses, so atomic weight does not always follow atomic number.
How did the discovery of new elements such as gallium help Mendeleev's table become accepted?
They fitted into gaps he had left, and their properties matched the ones he had predicted.
How is a metal defined in terms of the ions it forms?
A metal is an element that reacts to form positive ions.
How is a non-metal defined in terms of the ions it forms?
A non-metal is an element that does not form positive ions.
Where are metals and non-metals found in the periodic table?
Metals are to the left and towards the bottom; non-metals are towards the right and top.
Give three typical physical properties of metals.
Shiny, good conductors of heat and electricity, high melting and boiling points (also malleable and dense).
Give three typical physical properties of non-metals.
Dull, poor conductors of heat and electricity, low melting and boiling points (solids are brittle).
True or false? Most of the elements in the periodic table are non-metals.
False. The majority of elements are metals.
What are the elements in Group 0 called, and what is their key chemical property?
The noble gases — they are unreactive.
How many electrons are in the outer shell of a noble gas atom?
Eight, except helium, which has only two.
Why are the noble gases unreactive?
Their atoms have a stable arrangement of electrons (a full outer shell), so they do not share or transfer electrons.
What is the trend in boiling point going down Group 0?
Boiling point increases with increasing relative atomic mass (going down the group).
True or false? Helium has the lowest boiling point of the noble gases.
True. Boiling points increase down the group, and helium is at the top.
True or false? Noble gases exist as molecules made of pairs of atoms.
False. They do not easily form molecules — they exist as single (monatomic) atoms.
What are the Group 1 elements called, and what electron arrangement gives them their characteristic properties?
The alkali metals — they have a single electron in their outer shell.
What are the products when an alkali metal reacts with water?
e.g. potassium
A metal hydroxide and hydrogen.
Give three observations when a small piece of potassium is added to water.
It floats, melts and moves around on the surface; there is effervescence and a lilac flame, and the metal gets smaller.
What is formed when an alkali metal reacts with chlorine?
e.g. sodium
A white metal chloride salt.
What is formed when an alkali metal reacts with oxygen?
e.g. lithium
A metal oxide.
What is the trend in reactivity going down Group 1, and why?
Reactivity increases: the outer electron is further from the nucleus, so there is less attraction and the electron is lost more easily.
What are the Group 7 elements called, and how many outer electrons do their atoms have?
The halogens — seven outer electrons; they are non-metals made of molecules of pairs of atoms (e.g. ).
What is the trend in melting and boiling points going down Group 7, and why?
They increase: relative molecular mass and molecule size increase, so intermolecular forces are stronger and more energy is needed to overcome them.
What is the trend in reactivity going down Group 7, and why?
Reactivity decreases: the outer shell is further from the nucleus, so there is less attraction for an incoming electron and an electron is gained less easily.
What type of compound is formed when chlorine, bromine or iodine reacts with a metal?
An ionic compound — a metal halide salt containing halide ions, e.g. sodium chloride.
True or false? Chlorine and hydrogen react to form an ionic compound.
False. Halogens react with non-metals to form covalent molecular compounds, e.g. hydrogen chloride, .
What are the steps to write the equation for a halogen displacement reaction?
e.g. chlorine added to potassium bromide solution
- Check the added halogen is higher in Group 7 (more reactive): chlorine is above bromine, so a reaction happens
- Swap the halogens: potassium chloride + bromine
- Write and balance:
True or false? Bromine will displace chlorine from potassium chloride solution.
False. Only a more reactive halogen displaces a less reactive one, and chlorine is more reactive than bromine.