periodicity Flashcards
What are metalloids?
Elements that touch the stepped line dividing metals and non-metals, exhibiting both metallic and non-metallic properties.
Example: Silicon, which is a non-metal but has a shiny appearance and conducts electricity.
How are elements classified in the Periodic Table?
According to their position in the Periodic Table, determined by their proton number, as s, p, d, or f block.
What is a transition metal?
An element that forms a compound with a partly filled d-orbital.
Which d-block elements are not considered transition elements?
Zinc and scandium.
Zinc has a fully filled d-orbital and scandium has no electrons in the d-shell when a compound is formed.
What is the origin of the terms s, p, d, and f?
They come from spectroscopy, describing the lines produced when elements are heated and excited electrons fall back to lower energy levels.
What does ‘s’ stand for in the context of electron orbitals?
Sharp.
What trend is observed in reactivity in the S block?
Elements become more reactive as you go down a group.
What trend is observed in non-metals’ reactivity in the periodic table?
Non-metals become more reactive as you go up a group.
What ions do lanthanides tend to form?
3+ ions.
What characterizes actinides?
They are radioactive metals, with only thorium and uranium occurring naturally in significant quantities.
What is periodicity?
The characteristics of elements showing a repeating pattern and recurring variation with increasing atomic number.
What is the melting point trend for Na, Mg, and Al?
They exist as giant metallic structures, and their melting points increase due to more outer shell electrons and stronger attractions in the ‘sea’ of delocalised electrons.
What type of structure does silicon have?
Giant covalent molecule (macromolecular structure).
What type of forces do P, S, and Cl exhibit?
Weak van der Waals forces between simple molecules.
What is the atomic radius?
The distance between the centers of a pair of atoms, typically measured as half this distance.
What trend occurs in atomic radius across Period 3?
Atomic radius decreases as we move across the period due to increased nuclear charge pulling electrons closer.
What is the first ionisation energy?
The energy needed to remove one electron from each atom of an element in one mole of gaseous atoms to form one mole of gaseous ions with a 1+ charge.
What trend is observed in first ionisation energy across a period?
Generally increases, with exceptions between groups 2-3 and 5-6.
What is observed in first ionisation energy down a group?
It decreases due to larger atomic radius and increased shielding.
What causes the dip in ionisation energy between group 2 and 3?
Transition from S orbital to P orbital, resulting in increased shielding.
What causes the dip in ionisation energy between group 5 and 6?
In group 5, p subshell has one electron per orbital with no repulsion, while in group 6, one orbital has two electrons which repel each other.
What happens to successive ionisation energies when removing electrons?
They increase each time due to the increased difficulty of removing electrons from a positive ion.
What indicates a big jump in successive ionisation energies?
Breaking into an inner shell, which helps identify the group of the element.
