Chapter 1 - The Periodic Table Flashcards
What is an element?
A substance that cannot be split into two or more simpler substances by chemical processes or electricity
What does the proton (atomic) number represent?
The number of protons in the nucleus of an atom
What does the nucleon (mass) number represent?
The number of protons and neutrons in the nucleus of an atom
How are elements arranged in the Periodic Table?
Elements are arranged in order of their increasing proton (atomic) numbers
Metals are located on the ________ of the Periodic Table.
left and middle
Non-metals are located on the ________ of the Periodic Table
inclusive of ________ located at the top of the Periodic Table
right
hydrogen
Metalloids are located near the ________ between metals and non-metals
dividing line
What are the metalloids?
boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), polonium (Po), astatine (At)
How is the group number determined?
Determined by the number of valence electrons
What do elements in the same group have in common?
- Same number of valence electrons
- Similar chemical properties
Elements with 1, 2 or 3 valence electrons (metals) tend to ________ electrons to form ________ charged ions, or ________
lose
positively
cations
Elements with 5, 6 or 7 valence electrons (non-metals) tend to ________ electrons to form ________ charged ions, or ________
gain
negatively
anions
How is the period number determined?
Determined by the number of electron shells
What do elements in the same period have in common?
Same number of electron shells
Why do the atomic radii of the elements increase down the group gradually?
The number of electron shells or energy levels increases down the group as the number of electrons increases.
Each subsequent electron shell or energy level is further away from the nucleus which causes the outer electrons to be more shielded from the attraction of the nucleus (decrease in effective nuclear charge) and less strongly bound, therefore leading to increase of the atomic radii down the group.
Why are ionic radii for elements that form positive charge smaller while that for elements that form negative charge larger?
As electrons are removed from the outer shell to form positive ion, the attraction for the electrons increases which results in a decrease in ionic radius.
As electrons are added to the outer shell to form negative ion, the repulsion between the electrons causes the ionic radius to increase.
Define “metallic character”
The tendency of an element to lose electrons and form positive ions (cations)
Define “non-metallic character”
The tendency of an element to gain electrons and form negative ions (anions)
Properties of elements become ________ metallic down the group (i.e. elements lose electrons ________ easily).
more
more
Properties of elements become ________ metallic from left to right across the period (i.e. elements lose electrons ________ easily).
less
less
Properties of elements become ________ non-metallic from left to right across the period (i.e. elements gain electrons ________ easily).
more
more
Group I elements are known as the ________
alkali metals
What are the Group I metals?
lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), francium (Fr)
What are the physical properties characteristic of Group I metals?
- Are soft and can be cut by a knife
- Have a low density (lithium, sodium and potassium float on water)
- Have relatively low melting and boiling points
What are the physical properties of Group I metals that are typical of most metals?
- Are good conductors of heat and electricity
- Are shiny (seen only when alkali metals are freshly cut)
What is the physical properties trend of Group I metals?
- Softness ________ down the group
- Density ________ down the group
- Melting and boiling points ________ down the group
increases
increases
decrease
What are the chemical properties of Group I metals?
Are very reactive
What happens in the reaction of alkali metals with oxygen (oxidation)?
Alkali metals react with oxygen in the air to form metal oxides
alkali metal + oxygen → alkali metal oxide
Oxidation: The rate with which alkali metals react with oxygen in the air ________ down the group
- lithium – tarnishes ________
- sodium – tarnishes ________
- potassium – tarnishes ________
increases
slowly
quickly
very quickly
Oxidation: How are alkali metals stored?
Stored in oil to prevent them from reacting with oxygen and tarnishing
Oxidation: Equation for reaction of lithium with oxygen
lithium + oxygen → lithium oxide
4Li(s) + O2(g) → 2Li2O(s)
Oxidation: Equation for reaction of sodium with oxygen
sodium + oxygen → sodium oxide
4Na(s) + O2(g) → 2Na2O(s)
What happens in the reaction of alkali metals with water?
Alkali metal reacts with water to form a metal hydroxide
Reaction with water: Observations for reaction of lithium with water
- Reacts quickly with water
- Lithium floats on water
- No flame is seen
Reaction with water: Equation for reaction of lithium with water
lithium + water → lithium hydroxide + hydrogen
2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
Reaction with water: Observations for reaction of sodium with water
- Reacts very quickly with water
- Sodium dissolves and darts around the water surface
- A yellow flame is seen
Reaction with water: Observations for reaction of potassium with water
- Reacts violently with water
- Potassium dissolves and darts around the water surface very quickly
- A lilac flame is seen
Reaction with water: Observations for reaction of rubidium and caesium with water
Violent reactions, which may result in an explosion
What is the chemical properties trend of Group I metals?
- Reactivity ________ down the group
increases
Compounds of alkali metals:
- Have ________ chemical formulae
- Have ________ bonds
- Are ________ in water
similar
ionic
soluble
Group VII elements are known as the ________
halogens
What are the halogens?
fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At)
What are the physical properties of halogens?
Have low melting and boiling points
fluorine and chlorine are gases, bromine is a liquid and iodine is a solid at room temperature
Why do halogens have low melting and boiling points?
They exist as simple discrete molecules with only weak van der Waals’ forces between the molecules
What is the physical properties trend of halogens?
- Change from a ________ to a ________ down the group
- Colour becomes ________ down the group
- Melting and boiling points ________ down the group
gas, solid
darker
increase