Trends in the Periodic table.2 Flashcards
What are the elements in the periodic table arrangesd in order of
increasing atomic number
what are the vertical columns in the periodic table called
groups
horizontal rows
periods
what do elements in the same period have
have the same number of shells
what do elements in the same group have i common
have the same number of electrons in their outer shell/ valence shell
What is the name of group 1
Alkali metals
what valency do the Alkali Metals have?
valency of 1
Describe the reactivity of the Alkali Metals
highly reactive, before becoming more reactive going down the group
are Alkali metals found freely in nature?
not found freely in nature, only found in compounds with other elements
why are the alkali metals highly reactive
They do not satisfy the octet rule- they only have one electron in their valence shell.
In order to satisfy the octet rule they readily lose this electron when they react and form a monopostive ion.
why does reactivity of the alkali metals increase going down group 1
the atomic radius increases
List 3 properties of Alkali metals
soft metals- can be cut with a knife
low melting points and boiling points.
Have low densities - float on water
Describe the reactions of the alkali metals with oxygen
They react rapidly with oxygen to form a metal oxide.
for this reason they are stored in oil
what does an alkali metal + oxygen make
metal oxide
Describe the alkali metals reaction with water
Float on water.
React vigorouly with water.(reaction becomes more violent going down the group)
causes fizzing with water
produces a metal hydroxide and hydrogen gas
write a reaction for alkali metals with water
metal + water –> metal hydroxide + hydrogen
Demonstration of the reaction of the alkali metals lithium, sodium and potassium with water
all three metals float on water
each metal reacts vigorously with water
Fizzing occours due to hydrogen gas produced. This gas will ignite with a pop.
the reaction becomes more violent as the metals futhers down the group are added : sodium may spark and potassium catches fire.
what is group 2 called
The alkaline Earth Metals
what valency do the alkali earth metals have
have a valency of 2
describe the reactivity of the alkali earth metals
reqctive - but not as reactive as the alkali metals. become more reactive going down the group.
why are the alkaline earth metals reactive
they do not satisfy the octet rule - they have two electrons in their outwer shell in order to satisfy the octet rule, they readily lose these electrons when they react and form a dipostive ion (+2)
why does the reactivity of th alkaline earth metals increase going down group 2
the atomis radius increases
describe the reactivity of the alkaline earth metals with oxygen
the alkali metals react with oxygen to form a metal oxide, not as rapid as the alkali metals with oxygen
write a equaltion for the alkali earth metals reaction with oxygen
metal + oxygen –> metal oxide
describe the reactivity of the alkaline earth metals with water
they react with water to form a metal hydroxide and hydrogen gas.
Not as rapid or as vigorous a reaction as the alkali metals with water
write equation describing the reaction of alkaline metals with water
metal + water —> metal hydroxide + hydrogen
How is a transition metal identifies from its s,p configuration?
transition metals form at least one ion which has an incompelete 3d sublevel
Describe 3 features of Transition elements
they have variable valencies (Fe2+ or Fe3+)
they form compounds
they are excellent catalysts
What is a catalyst
a substance that alters the rate of a chemical reaction without being used up in the reaction
what elements are in the transition metal block but are not transition metals, and why?
Scandium and Zinc are not transition elements.
They do not have vairable valencies.
their compounds are white
they do not act as catalysts
what is group 7 called
The halogens
what valency do the Halogens have
valency 1
describe the reactivity of the Halogens
have seven electrons in their outer shell and are very reactive.They become less reactive going down the group. (form diatomic molecules - two atoms joined by a covalent bond)
why are the halogens reactive
They do not satisfy the octet rule - they have seven electrons in their valence shell. In Order to satisfy the octet rule, they gain one electron when they react and form a momonegative ion
why does the rectivity of the halogens descrease going down group 7
the atomic radius increases
what intermolecular forces occour between halogen molecules?
van der waals
Comment on the boiling points on the halogens
halogen molecules are non-polar - have weak van der waals forces between their molecules - have low boiling points.
As the molecules mass increases, the strnght of the intermolecular forces increases.
Fluorine (F2) and Chlorine (Cl2) are gases at room temperature
- Bromine (Br2) is a volatile liquid at room temperature
- Iodine (I2) is a volatile solid at room temperature
what is group 8 called
the nobel gasses
what valency do the noble gasses have
valency of 0
describe the reactivity of the halogens
they have eight electrons in their outer shell - this is a stable arrangement of electrons do not gain, lose, or share electrons - already satisfy the octet rule. Makes then very inert and safe to use.
Define atomic radius / convalent radius
half the distance between the nuclei of two atoms of the same element joined by a single covalent bond
State and explain the trend in atomic radii values (covalent radii) across a period of the periodic table
Atomic radii values decrease going across a period (Atoms get smaller)
The effective nucler charge increases- more protons in the nucleus means there is an increasng attraction between the nucleus and electrons in the outer shell, and the atom is being “pulled smaller”
State and explain the trend in atomic radii ( covalent radii) down a group of the periodic table
atomic radii values increase going down a group (atoms get larger). An additional shell of electrons is added on
Why is establishing an atomic covalent radius for the noble gasses problematic
The noble gasses satidy the octet rule- they do not gain, lose or share electrons so do not form bonds with other elements
What is electronegativity
the measure of reltive attraction an atom has for a shared pair of electrons in a covalent bond
state and explain the trend in electronegativity values across a period of the periodic table
electtronegativity calues increase going across a period.
1. The atomic radius decreases - pair of electrons in the covalent bond become closer to the postive nuclear charge
2. the effective nuclear charge increases- more protons in the nucleus means there is an increasing attracting between the nulceus and electrons in the covalent bond.
State and explain the trend in electronegativity values down a group of the periodic table.
Electronegativity values decrease going down a group.
1 the atomic radius increases- pair of electrons in the covalent bond become futher from the postive nuclear charge.
2. No increase in effective nuclear charge due to extra shell- electrons in covalent bond are more shielded from the nucleus.
Why do the noble gasses not have electronegative values
the noble gases satisfy the octet rule- they do not gain, lose, or share electrons so do not form bonds with other elements.
ionisation energy
the minimum energy required to remove the most loosely boind electron from an atom or ion
first ionisation energy
the minimim energy required to remove the most loosely bounf electron from a netural gaseous atom in the ground state
What is the first, second and third ionisation energy of potassium
K(g) —-> K+(g) + e-
K+(g) —> K2+ (g) + e-
K2+(g) —> K3+ (g) + e-
what is used to mesure ionisation energy
kilojoules per mole
State and explain the trend in first ionisation energy values across a period of the periodic table
the first ionisation energy values generally increase going across a period.
1. atomic radius decreases - the electron being removed becomes closer to the postive nuclear charge.
2. The effectve nuclear charge increases - more protons in the nucleus means there is an increasing attraction between the nucleus and the electron being removed.
State and explain the trend in first ionisation energy values down a group of the periodic table
First ionisation energy values decrease going down a group.
The atomic radius increases - electrons removed futher from the postive nuclear charge.
No increase in effecive nuclear charge due to an extra shell- most loosley bound electron is screened from the nucleus
Explain the exceptions to the general trend in energy values across a period
small decreases in ionsiation energies are due to electrons being removed from full sublevels, and half- full sublevels will require energy as these are high stability configurations
Explain the large substantial energy decreases going from one period to another
it takes substiantially less energy to remove an electron from a shell futher from the nucleus - this explains why there are large decreases in first ionisation energy going from one period to another
define second ionisation energy
the minium energy required to remove the most loosly bound electron from a postive ion
Give two reasons why the second ionisation energy of an element is a is always greater than the first
1- the second electron is being removed from a postive ion- the effective nuclear charge has incresed so there is greater sttraction between the electron being removed and the nucleus
2-The atomic radius has decreased in the postive ion - the second electron being removed is closer to the postive nuclear charge
How does looking at successive ionisation energy values for an element provide evidence for the exitance of energy levels
when attemption to remove an electron from a new energy level, a substantially higher amount of amount of energy is required.
looking at the number of substantial increases in ionisation energy will show how many energy levels are occupies by electrons in the atom
What other expeirmental evidence expect for ionisation energy do we have for the exitance of energy leves in atoms
line emission spectra
