3.1 Periodicity Flashcards
how is the modern periodic table arranged?
by atomic number
what groups are in s block on the periodic table?
1 and 2
what groups are in d block on the periodic table?
transition metals
what groups are in f block on the periodic table?
bottom two rows
what groups are in p block on the periodic table?
3, 4 ,5, 6, 7, 0
what is the definition of periodicity?
the regular repeating patterns in the physical and chemical properties of elements
what is the definition of ionisation?
when an atom loses an electron from its outer shell
what is the definition for first ionisation energy?
the energy required to remove one mole of electrons from one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
what is the first ionisation energy equation for sodium?
Na(g) —> Na+(g) + e-
what is the second ionisation energy equation for sodium?
Na+(g) —-> Na2+(g) + e-
what is the third ionisation energy equation for sodium?
Na2+(g) —-> Na3+(g) + e-
what can we learn from a successive ionisation energy graph?
what group an element is in - where the first big jump us shows number of electrons in outer shell
what are the 3 factors that affect ionisation energy?
shielding
nuclear charge
atomic radius
what is the definition of shielding?
the affect of the inner electrons shielding the outer electrons from the affect of the charge on the nucleus
what is the trend in shielding across period 3?
stays the same across period 3
what is the definition of nuclear charge?
the positive charge on the nucleus
what is the trend in nuclear charge across period 3?
increases across period 3
how do we measure atomic radius?
by measuring the distance between two nuclei of touching atoms and halving the distance
what is the trend in atomic radius across period 3?
decreases across period 3 - and other periods
why does the atomic radius decrease across period 3?
the nuclear charge increases, the shielding stays the same, the nuclear attraction increases so the atomic radius decreases
what is the general trend of ionisation energy in group 3?
increases across period 3
explain the general trend of ionisation energy in group 3
the nuclear charge increases, the atomic radius decreases, the nuclear attraction increases, the shielding stays the same - it takes more energy to remove the first electron
why does first ionisation energy decrease between magnesium and aluminum?
aluminum has one electron in a higher subshell (3p), this one electron is removed more easily as it is further away from the nucleus, therefore the first ionisation energy is lower than magnesium
why does the first ionisation energy go down between phosphorous and sulphur?
sulphur has one 3p orbital that contains a pair of electrons - these paired electrons repel each other, so one of these electrons is easier to remove therefore sulphur has a lower ionisation energy than phosphorous
what is the trend for shielding and nuclear charge down group 2?
they both increase down the group
what is the trend for atomic radius down group 2?
increases down the group
what is the explanation for atomic radius increasing down group 2?
shielding increases, nuclear charge increases but is cancelled out by the extra shielding
so the nuclear attraction decreases and atomic radius gets bugger
what is the trend in first ionisation energy down group 2?
decreases down the group
what is the explanation for the trend in first ionisation energy down group 2?
decreases down the group because there is an increase in shielding, an increase in nuclear charge, nuclear attraction of the electrons to the nucleus decreases, atomic radius increases so less energy is required to remove the outer electron
What is the arrangement of elements in the periodic table?
Elements are arranged in increasing atomic number
This arrangement reflects the periodic law and the structure of the atomic nucleus.
What do elements in the same group have in common?
Similar physical and chemical properties
This similarity arises from having similar outer shell electron configurations.
How are elements classified in the periodic table?
Elements are classified as s, p, or d block
The classification depends on which orbitals the highest energy electrons are in.
What is periodicity in terms of elements?
A repeating pattern across different periods
This pattern includes trends in physical and chemical properties.
What is the trend of atomic radius across a period?
Atomic radii decrease from left to right across a period
This decrease is due to increased positive charge attraction from protons.
What is the first ionisation energy?
Energy needed to remove an electron from each atom in one mole of gaseous atoms
The process is always considered in the gaseous state.
What factors affect ionisation energy?
- The attraction of the nucleus
- The distance of the electrons from the nucleus
- Shielding of the attraction of the nucleus
Each of these factors influences how tightly electrons are held by the nucleus.
Why are successive ionisation energies always larger?
The ion formed is smaller than the atom, resulting in a greater proton to electron ratio
This leads to stronger attraction between the nucleus and remaining electrons.
What does a big jump between successive ionisation energies indicate?
It indicates a change in the electron shell being removed
For example, if there’s a large jump between the 2nd and 3rd ionisation energies, it suggests that the 3rd electron is removed from an inner shell.
Fill in the blank: The attraction of the nucleus is greater when there are more ______.
protons
A greater number of protons increases the positive charge, enhancing attraction.
True or False: The first ionisation energy can vary based on the physical state of the atom.
False
The first ionisation energy is always considered for gaseous atoms.
What does a large ionisation energy suggest about an element’s group?
It suggests the element is in Group 2 if there is a large jump between the 2nd and 3rd ionisation energies
This is due to the removal of an electron from a shell closer to the nucleus.
List the elements in Period 2.
Li, Be, B, C, N, O, F, Ne
These elements display trends in properties across the period.
List the elements in Period 3.
Na, Mg, Al, Si, S, Cl, Ar
Similar to Period 2, these elements also exhibit periodic trends.
What is periodicity in relation to ionisation energy?
A repeating pattern across a period.
What useful information does the pattern in first ionisation energy provide?
Information about electronic structure.
Why does Helium have the largest first ionisation energy?
Its first electron is closest to the nucleus with no shielding effects.
Why do first ionisation energies decrease down a group?
Outer electrons are further from the nucleus and more shielded.
What generally happens to first ionisation energy across a period?
It increases.
Why does first ionisation energy increase across a period?
Number of protons increases, enhancing nuclear attraction.
Why does Na have a much lower first ionisation energy than Neon?
Na’s outer electron is in a 3s shell, further from the nucleus and more shielded.
What causes the small drop in ionisation energy from Mg to Al?
Al begins to fill a 3p subshell, which is easier to remove compared to 3s.
Why is there a small drop in ionisation energy from P to S?
The 4th electron in sulfur causes slight repulsion in the 3p orbital.
What are the three factors that control ionisation energy?
Nuclear charge, distance from nucleus, and shielding effect.
Fill in the blank: The first ionisation energy is the energy required to remove an electron from a _______.
neutral atom.
True or False: The number of protons in an atom affects its ionisation energy.
True.
Fill in the blank: Electrons in the same orbital must have _______ spins.
opposite.
What happens when the second electron is added to a 3p orbital?
There is slight repulsion between the two negatively charged electrons.
What is metallic bonding?
The electrostatic force of attraction between the positive metal ions and the delocalised electrons
This type of bonding is characteristic of metals.
What are the three main factors that affect the strength of metallic bonding?
- Number of protons/Strength of nuclear attraction
- Number of delocalised electrons per atom
- Size of ion
Each factor contributes to the overall strength of the metallic bond.
How does the number of protons affect metallic bonding?
The more protons, the stronger the bond
Protons contribute to the nuclear attraction in metallic bonding.
How does the number of delocalised electrons per atom affect metallic bonding?
The more delocalised electrons, the stronger the bond
Delocalised electrons are the outer shell electrons that participate in bonding.
How does the size of the ion affect metallic bonding?
The smaller the ion, the stronger the bond
Smaller ions can get closer to the delocalised electrons, increasing attraction.
Which metal has stronger metallic bonding, Mg or Na?
Mg
Mg has more electrons in the outer shell and a smaller ion size, leading to stronger bonding.
What is a macromolecular structure?
Giant molecular structures
Examples include diamond and graphite.
Describe the arrangement of carbon atoms in diamond.
Tetrahedral arrangement with 4 covalent bonds per atom
This structure contributes to diamond’s hardness.
Describe the arrangement of carbon atoms in graphite.
Planar arrangement with 3 covalent bonds per atom in each layer; delocalised electrons between layers
This allows layers to slide over each other, making graphite slippery.
Why do macromolecular structures like diamond and graphite have very high melting points?
Because of strong covalent forces in the giant structure
It takes a lot of energy to break the many strong covalent bonds.
What type of bonding is described as the electrostatic force of attraction between positive metal ions and delocalised electrons?
Metallic bonding
This is a characteristic feature of metals.
What are some examples of macromolecular structures?
- Diamond
- Graphite
- Silicon dioxide
These structures are known for their strong covalent bonds.
Fill in the blank: _____ is a type of bonding where a shared pair of electrons is involved.
Covalent
Covalent bonding occurs between non-metals.
What is the structure of metallic bonding called?
Giant metallic lattice
This lattice structure is characteristic of metals.
What type of bonding is present in macromolecular structures?
Covalent bonding
Macromolecular structures have many strong covalent bonds that require a lot of energy to break.
How do the boiling and melting points of macromolecular substances compare?
High
Due to many strong covalent bonds in their structure.
What is the solubility of macromolecular substances in water?
Insoluble
Macromolecular substances do not dissolve in water.
What is the conductivity of macromolecular substances when solid?
Poor
Electrons are localised and cannot move.
What is the conductivity of graphite?
Good
Graphite has free delocalised electrons between layers, allowing for conductivity.
What is the general description of giant metallic structures?
Shiny metal, malleable
The identical positive ions allow planes of ions to slide over each other easily.
What type of bonding is present in giant metallic structures?
Metallic bonding
Strong electrostatic forces between positive ions and a sea of delocalised electrons.
What is the solubility of giant metallic substances in water?
Insoluble
Giant metallic structures do not dissolve in water.
How does the conductivity of giant metallic substances compare when molten?
Good
Delocalised electrons can move through the structure when molten.
What is the melting and boiling point trend for Na, Mg, and Al?
High melting and boiling points
Due to strong metallic bonding that increases with more electrons released to the sea of electrons.
What is the melting point of Si and why?
Very high
Si is macromolecular with many strong covalent bonds requiring a lot of energy to break.
What type of forces are present in simple molecular substances like Cl2 and Sg?
Weak London forces
These weak forces require little energy to break, resulting in low melting and boiling points.
Why does Se have a higher melting point than P4?
More electrons
Se has stronger London forces due to having more electrons.
What type of forces are present in monoatomic gases like Ar?
Weak London forces
These forces result in very low melting points.
What trend is observed in period 2 for Li and Be?
Metallic bonding with high melting points
Both elements exhibit strong metallic bonding.
What type of bonding is observed in B and C?
Macromolecular
They have very high melting points due to strong covalent bonds.
What type of substances are N2 and O2?
Molecular gases
They have low melting points due to small London forces.
What is the melting point of Ne?
Very low
Ne is a monoatomic gas with weak London forces.
What happens to the atomic radius as one goes down Group 2?
Atomic radius increases down the Group.
Atoms have more shells of electrons making the atom bigger.
What is the outer shell electron configuration for Group 2 metals?
Outer shell s² electron configuration.
This configuration is common among all Group 2 metals.
How do melting points change down Group 2?
Melting points decrease down the group.
This is due to weakening metallic bonding as atomic size increases.
What causes the weakening of electrostatic attractive forces in Group 2 metals?
The distance between positive ions and delocalized electrons increases.
This results in weaker attractive forces.
What happens to ionization energies as one moves down Group 2?
First and second ionization energies decrease down the group.
This is due to outermost electrons being further from the nucleus and more shielded.
Define first ionization energy.
Energy needed to remove an electron from each atom in one mole of gaseous atoms.
Represented by the equation: H(g) → H⁺(g) + e⁻.
What is the second ionization energy?
Enthalpy change when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge.
Represented by the equation: Ti⁺(g) → Ti²⁺(g) + e⁻.
How does reactivity change in Group 2 metals?
Reactivity increases down the group.
This is due to increased atomic radii and more shielding.
What occurs when Group 2 metals react with oxygen?
They burn in oxygen.
Mg burns with a bright white flame producing MgO.
What is the reaction equation for magnesium burning in oxygen?
2Mg + O₂ → 2MgO.
MgO is a white solid with a high melting point due to ionic bonding.
What happens to magnesium ribbon when exposed to oxygen?
It often has a thin layer of magnesium oxide on it.
This layer forms slowly and needs to be cleaned before reactions.
What is the significance of cleaning magnesium ribbon before reactions?
An uncleaned Mg ribbon would give a false result in reaction rate tests.
Both Mg and MgO would react but at different rates.
What is the reaction equation for magnesium reacting with hydrochloric acid?
Mg + 2HCl → MgCl₂ + H₂.
This illustrates the reaction of magnesium with acid.
What is the reaction equation for magnesium oxide reacting with hydrochloric acid?
MgO + 2HCl → MgCl₂ + H₂O.
This shows the reaction of magnesium oxide with acid.
