P Block Board Flashcards
What is the general electronic configuration of Group 16 elements?
ns2np4
Group 16 elements are also known as the oxygen family or chalcogens.
What is the first element of Group 16?
Oxygen (O)
Oxygen is atomic number 8.
What is the first element of Group 17?
Fluorine (F)
Fluorine is atomic number 9.
What is the first element of Group 18?
Helium (He)
Helium is atomic number 2.
What are the elements of Group 17 collectively known as?
Halogens
The term ‘halogen’ comes from Greek, meaning ‘salt-producing’.
Why are halogens highly reactive?
Due to high electronegativities
Halogens are not found in free state but occur in compounds.
What is the most abundant element on Earth?
Oxygen
Oxygen makes up 20.95% by volume of air and about 46.6% by mass of the Earth’s crust.
What are other names for group 16 elements
- Oxygen family
- Chalcogens
Group 16 elements include sulfur, selenium, tellurium, and polonium.
What is the electronic configuration of noble gases in Group 18?
ns2np6
This configuration indicates a stable electronic arrangement.
What is the trend in atomic and ionic radii within Groups 16, 17, and 18?
Increase down the group
This is due to an increase in the number of quantum shells.
How does ionization enthalpy change across a period?
Increases with increasing atomic number
This is due to increased effective nuclear charge.
What is the trend in electronegativity within Groups 16, 17, and 18?
Decreases down the group
Electronegativity reflects the ability of an atom to attract electrons.
What is the electron gain enthalpy trend in Groups 16 and 17?
Becomes less negative down the group
This trend indicates a decrease in the tendency to accept electrons.
Why does oxygen have less negative electron gain enthalpy than sulfur?
Smaller atomic size
Smaller size leads to higher electron-electron repulsion.
What is the bond dissociation enthalpy order of halogen molecules?
- Cl - Cl >
- Br - Br >
- F - F >
- I - I
This order is due to the strength of the bonds influenced by atomic size.
What phase are fluorine and chlorine at room temperature?
Gases
Bromine is a liquid and iodine is a solid at room temperature.
What is the atomic radius of oxygen?
66 pm
This is the atomic radius of oxygen in picometers.
What is the ionization enthalpy of fluorine?
1680 kJ/mol
Fluorine has the highest ionization enthalpy among the halogens.
What is the melting point trend of elements in Groups 16, 17, and 18?
Increases with increasing atomic number
This trend is influenced by the strength of intermolecular forces.
What type of elements are selenium and tellurium classified as?
Metalloids
They have properties of both metals and nonmetals.
What is the significance of the half-life of polonium?
Radioactive element with a half-life of 13.8 days
Polonium is a decay product of thorium and uranium.
What is the electron gain enthalpy of fluorine compared to chlorine?
Less negative
Fluorine’s small size causes stronger electron-electron repulsion.
What is lone pair-lone pair repulsion?
Repulsion that occurs between non-bonding pairs of electrons in a molecule
This concept is important in molecular geometry and affects the shape of molecules.
What trend is observed in melting and boiling points with increasing atomic number in group 16 elements?
Melting and boiling points increase
This trend is due to the increase in van der Waals forces as atomic size increases.
Why is there a large difference between the melting and boiling points of oxygen and sulfur?
Oxygen exists as a diatomic molecule (O2), whereas sulfur exists as a polyatomic molecule (S8)
The van der Waals forces are weaker in O2 compared to the stronger forces in S8 due to larger molecular size.
What are the characteristics of noble gases?
- Monoatomic
- Sparingly soluble in water
- Very low melting and boiling points
Helium has the lowest boiling point of any known substance at 4.2 K.
What causes the low melting and boiling points of noble gases?
They are monoatomic with only van der Waals forces between them
This allows them to be liquefied at very low temperatures.
What is the atomicity of oxygen compared to other group 16 elements?
Oxygen is a diatomic molecule (O2), while others are polyatomic
For example, sulfur exists as S8.
What is the common covalency of oxygen?
2, but can be 4 in rare cases
Other group 16 elements can exceed a covalency of four.
What are the reasons for the anomalous behavior of oxygen?
- Small atomic size
- High electronegativity
- Absence of inner d-orbitals
These factors influence its chemical behavior compared to other group 16 elements.
What distinguishes the oxidation states of oxygen from those of other group 16 elements?
Oxygen shows -2, -1, and +2 oxidation states, while others show -2, +2, +4, +6
Oxygen cannot exhibit higher oxidation states due to the absence of vacant d orbitals.
What is the trend in oxidation states for group 17 elements?
Halogens exhibit -1 oxidation state; Cl, Br, I can also show +1, +3, +5, +7 due to empty d-orbitals
Fluorine only exhibits -1 due to its high electronegativity.
What is the stability trend of halides?
Fluorides > Chlorides > Bromides > Iodides
This trend is influenced by bond strength and electronegativity.
What type of compounds do group 16 elements form with hydrogen?
Hydrides of the type H2E
Where E represents elements like O, S, Se, Te, Po.
What is the acidic strength trend of hydrogen halides?
HF < HCl < HBr < HI
This order is due to decreasing bond dissociation enthalpy.
What are the properties of the hydrides of group 16 elements?
- H2O is colorless and odorless
- H2S, H2Se, H2Te, and H2Po are colorless gases with bad odors
- Weakly acidic
The acidic character increases down the group.
What is the reactivity of group 18 elements towards hydrogen?
Noble gases are chemically inert due to their stable electronic configuration
They do not form hydrogen halides.
What type of oxides do group 16 elements form?
- EO2
- EO3
Where E represents elements like S, Se, Te, Po.
What is the property of fluorine oxides?
Fluorine forms two oxides OF2 and O2F2, with OF2 being thermally stable
Both are strong fluorinating agents.
How do group 17 elements react with halogens?
They form interhalogen compounds of types XX’, XX’5, and XX’7
Where X is a larger halogen and X’ is a smaller halogen.
What is the significance of d-orbitals in xenon?
Xenon can exhibit higher oxidation states due to the presence of d-orbitals
This allows for the formation of covalent compounds with fluorine or oxygen.
What is the general formula for the reaction of group 17 elements with hydrogen?
H2 + X2 → 2HX
Where X represents halogens such as F, Cl, Br, and I.
What is the photocopying process?
A selenium-coated rotating drum is given a uniform positive charge, exposed to an image, negatively charged toner particles are attracted, and the image is transferred to paper and fixed by heating.
The drum is then cleaned and prepared for another cycle.
What do elements of group 17 (Halogens) react with metals to form?
Metal halides
Example: 2Na (s) + Cl2 (g) → 2NaCl (s)
What is the order of ionic character of halides?
MF > MCl > MBr > MI
M is a monovalent metal.
How does the oxidation state of metals affect the covalent character of metal halides?
Higher oxidation states lead to more covalent character.
Example: SnCl4 is more covalent than SnCl2.
Do noble gases (Group 18) directly react with metals?
No
Noble gases are generally inert.
What is allotropy?
The existence of an element in more than one form in the same physical state.
Example: Oxygen has O2 and O3.
What is the difference between allotropy and polymorphism?
Allotropy refers to different forms of an element, while polymorphism refers to different forms of a compound.
Both concepts involve variations in structure.
What are the allotropes of sulfur?
Rhombic sulfur (α-sulfur) and monoclinic sulfur (β-sulfur)
Both are non-metallic and have distinct properties.