Free TCE Year 11 Physical Sciences Flashcard Review
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Shell configuration of potassium (Z = 19)?
2,8,8,1: four shells, so period 4; one outer electron, so group 1.
Why does atomic radius decrease across period 3?
Nuclear charge increases while electrons are added to the same shell, so outer electrons are pulled closer to the nucleus.
Why does atomic radius increase down group 1?
Each element down the group has one more occupied electron shell.
What charge does a stable ion of a group 17 element carry?
1−, because the atom gains one electron to complete its outer shell of eight.
How many neutrons are in ¹³₆C?
13 − 6 = 7 neutrons.
Why do carbon-12 and carbon-14 react the same way?
They have the same number of electrons in the same shells, so their chemical properties are the same.
What two pieces of information does each peak in a mass spectrum give?
Its position gives the isotopic mass (mass-to-charge ratio) and its height gives the relative abundance.
Effect of beta-negative decay on A and Z?
A is unchanged and Z increases by 1, because a neutron becomes a proton and an electron is emitted.
What does the m in technetium-99m indicate?
A metastable nucleus with excess energy that releases it as a gamma photon without changing A or Z.
Rank alpha, beta and gamma by ionising ability.
Alpha is the most ionising, then beta, then gamma; penetrating power is in the reverse order.
Controlled versus uncontrolled chain reaction?
Controlled: control rods absorb surplus neutrons for steady heat in a reactor. Uncontrolled: fissions multiply rapidly for an explosive release.
Fraction remaining after 3 half-lives?
(½)³ = 1/8 of the original amount.
Distance versus displacement?
Distance is the total path length (scalar); displacement is the straight-line change in position with a direction (vector).
What does the slope of a displacement-time graph give?
The velocity at that moment (the slope of the tangent gives instantaneous velocity).
What does the area under a velocity-time graph give?
The displacement over that time interval.
Which equation of motion has no time in it?
v² = u² + 2as.
Acceleration of a ball at the top of its flight when thrown straight up?
9.8 m s⁻² downwards; only the velocity is momentarily zero.
Why does a skydiver reach terminal velocity?
Air resistance increases with speed until it equals the weight, so the net force and acceleration become zero.
In a horizontal projectile, what happens to the horizontal velocity?
It stays constant (ignoring air resistance) because there is no horizontal force.
What decides the time of flight of a horizontally launched projectile?
Only the vertical drop height, using s = ½gt².