period 3

Created by

Georgia Forbes

Cards (41)

what are the 3 types of elements on the periodic table?
metals
non-metals
metalloids
where are the metals on the periodic table? 
metals are in the centre and the left side
where are the non-metals on the periodic table?
non-metals are on the right side
what are metalloids? 
metalloids are elements that display some properties which are characteristics of metals and some properties which are characteristics of non-metals.
where are metalloids found on the periodic table?
metalloids are found alongside the line that divides the metals from the non-metals
what are 2 examples of metalloids?
boron
silicon
alongside their chemical symbol, what is the higher of the 2 numbers?
the higher of the 2 numbers tells you the elements relative atomic mass.
alongside their chemical symbol, what is the lower of the 2 numbers?
the lower of the 2 numbers is the proton number and gives the number of protons present in the element's nucleus.
what is relative atomic mass?
the average mass of an atom of an element on a scale where an atom of carbon 12 is 12
how are elements on the periodic table arranged?
arranged in order of proton number
aside from proton number, how else is the periodic table split?
into blocks of s, p, d and f
where is the s block?
far left, groups 1 and 2
where is the d block?
transition metals
where is the p block?
non-metals, far right
where is the f block?
right at the bottom, beneath the other blocks.
how do we decide which element is in which block?
it depends on their position in the periodic table.
their position is determined by their proton number and tells us the orbital in which their outermost electron is found.
eg: what block is sodium?
sodium has an electron configuration of : 1s2 , 2s2 , 2p6 , 3s1
sodium's outermost electron is in an s orbital
so sodium is in the s-block.
how can we describe the position of an element in the periodic table?
using its group number
using its period number
describe a group of the periodic table
each group in the periodic table is a vertical column of elements which all have the same number of electrons in the outermost shell.
elements in the same group show trends in physical properties and similarities in their chemical properties.
describe a period of the periodic table
periods are horizontal rows in the periodic table.
the period number of an element gives the number of the outermost energy shell containing electrons.
what occurs as we move across the periods?
there are repeating patterns/trends in the physical and chemical properties of the elements.
what is another phrase for a repeating pattern?
a periodic pattern
across period 3, what are the patterns?
atomic radius
ionisation energy
melting points
what is the summary of the melting point trend across period 3?
across period 3, there is an increase in melting point over the 1st 3 metallic elements ( Na, Mg and Al ).
Si has a high melting point
the next 3 elements, decrease in melting point.
describe the melting point in the 1st 3 metallic elements in period 3
there is an increase in melting point over the 1st 3 metallic elements.
metals have a giant metallic lattice structure made of positively charged metal ions and a sea of delocalised electrons.
the strength of the metallic bond is determined by the number of electrons delocalised per atom.
in Na, only 1 electron is delocalised per atom
in Mg, 2 electrons are delocalised per atom
in Al, 3 electrons are delocalised per atom.
so, Al mp > Mg mp > Na mp
describe the melting point in the 4th period 3 element (Si)
Si is a non-metal with a macromolecular structure where each silicon atom is joined to 4 others through covalent bonding.
covalent bonds are very strong and there are so many of them so a large amount of energy is needed to break down their structure.
so, silicon has a very high melting point.
describe the melting point of the last 3 elements in period 3 (P, S and Cl)
they bond thorough covalent bonding but form simple molecules.
the stronger the intermolecular forces of attraction between molecules, the higher the melting point.
P forms P4 molecules, S forms S8 molecules and Cl forms Cl2 molecules.
all these molecules have van Der Waals forces acting between them, the larger the molecules the stronger the Van Der Waals forces.
p4 molecules is smaller than S8, so S8 has a higher melting point.
Cl2 is smaller than both, so has a lower melting point than them both.
describe the melting point for the last element in period 3 (Ar)
Ar has the lowest melting point in period 3
this is because Ar exists only as single atoms with no intermolecular forces acting between them.
what is the atomic radius?
the distance between the nucleus and the outermost shell of electrons
how do we determine atomic radius?
the number of electron shells present and the force of attraction between the outermost electrons and the protons in the atom's nucleus.
describe how the atomic radius can be small
if the force of attraction between the outermost electrons and the proton in the nucleus is great then the electrons are held more tightly to the nucleus and the atomic radius is smaller.
how can the shielding affect effect atomic radius?
as more shells of electrons are added between the outermost electrons and the atom's nucleus, the force of attraction between the protons in the nucleus and the outermost electrons decreases.
this is the shielding effect.
the more shells that are between nucleus and outermost electrons, the greater the shielding effect and the weaker the force of attraction is.
so, the outermost electrons are held less tightly to the nucleus and the atomic radius becomes larger.
how does atomic radius change across period 3? 
atomic radius decreases as we move across period 3
why does atomic radius decrease across period 3?
as we move across period 3 from Na to Ar, the number of protons in the nucleus increases which results in a higher positive charge in the nucleus.
the number of electrons increases across the period but the outermost elections are added to the same energy shell so the shielding effect is pretty constant.
the increase in positive charge in the nucleus results in a stronger force of attraction between nucleus and outermost electrons. The outermost electrons are pulled in closer to the nucleus and the atomic radius decreases.
what is first ionisation energy?
first ionisation energy = the energy needed to remove 1 electron from 1 mole of gaseous atoms to form 1 mole of gaseous ions.
what is the equation which represents first ionisation energy?
X (g) --> X+(g) + e-
x = an atom of any elemtn
X+ = the positive ion made when an electron is lost from the atom
what is the general trend of ionisation energy across period 3? 
there is a general increase in first ionisation energy as we move across period 3
why does the ionisation energy increase generally across period 3?
as we move across the period, there is an increase in protons causes an increase in positive charge on the nucleus and results in a stronger force of attraction between the nucleus and outermost electrons.
the outermost electrons are pulled in closer to the nucleus and atomic radius decreases.
the stronger force of attraction between outermost electrons and nucleus means more energy needed to overcome this force of attraction and remove the electron so 1st ionisation energy increases.
what are the 2 clear deviations in the increase in ionisation energy in period 3?
Mg and Al
P and S
explain the deviation between magnesium and aluminium in ionisation energy in period 3
Mg's electron configuration : 1s2 , 2s2 , 2p6 , 3s2.
Al's electron configuration : 1s2 , 2s2 , 2p6 , 3s2 , 3p1.
Mg's outermost electron is in a 3s orbital and Al's outermost electron is in a 3p orbital.
3s orbital is closer to nucleus than the 3p orbital.
the 3p orbital's electron is held less tightly to the nucleus than the ones in 3s so it takes less energy to remove the 3p electron form the atom and the 1st ionisation energy is lower.