Chemistry Unit 1 After Mid Flashcards
What is the aufbau( building up ) principle
It’s a scheme used to reproduce the electron configurations of the ground state of atoms by successively filling with electron in a specific order (the building up order)
It states that electrons occupy the lowest-energy orbital available before entering the higher energy orbital.
What does hunds principle state
Equal energy orbitals (degenerate orbitals) are each occupied by a single electron before the second electrons of opposite spin enters the orbital
What does paulis exclusion principle state
No two electrons can have the same four quantum numbers
What does electron configuration describe
It describes the distribution of electrons among atomic orbitals
Electrons in the outermost principal quantum level of an atom is called
Valance electrons
The inner electrons are known as
Core electrons
__________ are the most important electrons since they are involved in bonding
Valance electrons
To avoid writing the inner electrons
We abbreviate the sub shell notation by using noble gases
Why is the expected configuration of chromium and copper, based on the Aufbau principle, not observed through the emission spectra and magnetic properties of these elements.
it seems that the half-filled 3d subshell of chromium (3d5) and the fully filled 3d subshell of copper (3d10) lends a special stability to the electron configurations.
At higher principal quantum numbers, the energy difference between certain subshell is even smaller than that between the 3d and 4s subshells. As a result,
there are still more exceptions to the Aufabu principle among the heavier transition elements
What the periodic law state
the periodic law states that certain sets of physical and chemical properties recur at regular intervals (periodically) when the elements are arranged according to increasing atomic number
Why do elements in the same group have similar chemical behaviour
Because they have the same valance electrons
What does the period indicate
It indicates the value of n for the outermost or valence shell
How many periods and groups are there in the periodic table
There are 18 groups and 7 periods
Why can’t we measure the exact size of an electron and how do we measure the estimate size?
- It can be measured because electron cloud surrounding the atom does not have a sharp boundary.
- it’s estimate size is measured by measuring the distance between the nuclei of two adjacent atoms
Variations in atomic size are a result of
- change in the principal quantum number
- changes in the effective nuclear charge
What is the trend of atomic radius in transition elements
- Because electrons enter an inner electron shell, not the valence shell As we move from left to right, size shrinks through the first two or three transition elements because of the increasing nuclear charge. But, from then on, the size remains relatively constant because shielding by the inner d electrons counteracts the usual increase in Zeff.
What is ionization energy
- is the energy (in kJ) required for the complete removal of 1 mol of electrons from 1 mol of gaseous atoms or ions
_____________ of an atom is the minimum energy needed to remove the highest-energy (that is, the outermost) electron from the neutral atom in the gaseous state.
- the first ionization energy
Why is the secound ionization energy always larger than the first
- Because the electron is being pulled away from a positively charged ion
The first ionization energy is a key factor in an element’s chemical reactivity because
atoms with a low IE1 tend to form cations during reactions, whereas those with a high IE1, (except the noble gases) often form anions.
The lowest and highest ionization energy are
- lowest = alkali metals
- Highest= noble gas elements
Why does ionization energy increase across a period?
- as we go across a period the effective nuclear charge increases therefore the ionization energy increases
List the deviations in ionization energy trend and explain
- group 3 has a smaller ionization energy than group 2 because, group 3 is ns2 np1 and group 2 is ns2
the np is easily removed that the ns - group 6 has a smaller ionization energy than group 5 because group 6 is ns2np4 and group 5 is ns2 np3 and As a result of electron repulsion, it is easier to remove an electron from the doubly occupied np orbital of the 6 element than from a singly occupied orbital of the preceding 5 element.
