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Flashcards in Periodic Table Deck (177)
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What is the modern periodic table arranged in?

By order of proton number


What are Döbereiner triads?

The groups that were made when, in 1817, Johann Döbereiner attempted to group similar elements


What did the English chemist, John Newlands, notice when her arranged the elements in order of mass?

That elements with similar chemical and physical properties occurred at regular intervals, but every 8th element was different


What did Newlands call his discovery?

The law of octaves


What does the Periodic law state?

If you arrange the elements in order of increasing atomic number then their chemical and physical properties will repeat in a systematic way


What was different about Mendeleev's table?

He left gaps, so that elements with similar properties were in the same group


Give an example of a case where 2 elements in the periodic table are the wrong way around?

Ar ----> K are not in order of atomic mass


All the elements within the same period have the same number of...



What is periodicity?

A repeating pattern of physical and chemical properties across a period


Why is the sub-shell 4s before 3d?

The 4s sub-shell has a lower energy level


What is the electron configuration of cobalt (27 electrons)

1s2 2s2 2p6 3s2 3p6 4s2 3d7


What is the first ionisation energy?

The energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms


What type of process is the first ionisation energy?

Endothermic, as you have to put energy in to remove the 1st electron


Write out the 1st ionisation energy equation of oxygen

O -----> O+ + E-


Why do you have to use the gas state symbol when writing out the equation for the first ionisation energy?

Because ionisation energies are measured for gaseous atoms


The lower the ionisation energy...

The easier it is to form an ion


What is an endothermic process?

One that takes in heat


What does a high ionisation energy mean?

There's a strong electrostatic attraction between the electron and nucleus, so more energy is needed to remove the first electron


What 3 things affect ionisation energy?

Nuclear charge
Atomic radius


How does nuclear charge affect ionisation energy?

The more protons there are in the nucleus, the more positively charged it is and so the stronger the attraction for the electrons


How does atomic radius affect ionisation energy?

Attraction falls off rapidly with distance, so an electron closer to the nucleus will be more strongly attracted than one that's further away


How does shielding affect ionisation energy?

As the number of electrons between the outer electrons and the nucleus increases, the outer electrons feel less attraction


What is the trend in ionisation energy down a group?

As you go down a group, ionisation energies decrease (as it gets easier to remove an electron)


Why does ionisation energy decreases down a group?

Elements further down a group have extra electron shells, so the atomic radius is larger (reducing attraction to the nucleus). Shielding also increases


What is the trend of ionisation energies as you go along a period?

They increase (gets harder to remove the outer electrons)


Why do the ionisation energies increase as you go along a period?

Number of protons increases, meaning a larger nuclear charge, so a smaller atomic radii and a stronger attraction


Is there any shielding change as you go along a period?

No, as all the extra electrons are at roughly the same energy level


As you go along a period, why is there a drop of ionisation energy between Group 2 and 3?

Due to the outer electrons in Group 3 being in a p-orbital rather than an s-orbital


As you go along a period, why is there a drop of ionisation energy between Group 5 and 6?

Due to electron repulsion


Why does electron repulsion cause a drop of ionisation energy between Group 5 and 6?

For the Group 5, the outer electron is being removed from an orbital containing 1 electron, whereas for the Group 6, the outer electron is being taken from an orbital containing 2 electrons (which repel each other). This repulsion makes it easier to remove an electron