period table & trends Flashcards
elements in a periodic table are arranged in what order?
increasing proton number
period number =?
number of electron shells
group number=?
no. of valence electrons (outer shell electrons)
what happens across the periodic table?
the metallic character decreases and elements are less likely to lose its valence electrons
what happens down the group?
the atomic radius increases as the number of electron shells increases
what are group 1 metals called and why?
group 1 metals are called alkali metals because they react with water to form an alkali solution
what are the physical properties of group 1 alkali metals?
soft (can be cut easily), low melting and boiling point, low density, good conductor of electricity and heat
they react with water to form an alkali solution and hydrogen gas
they form white-coloured compounds that dissolve in water to give a colourless solution
what are the trends down group 1?
density generally increases, reactivity increases, melting and boiling point decreases
down group 1, why are the valence electrons more easily lost?
down group 1, the number of electrons increases. this means that the valence electron is further away from the nucleus and the attraction force between the valence electron and the protons in the nucleus decreases. hence, valence electrons are more easily lost, and reactivity increases.
what are group VII elements?
group VII elements are non-metals and they are called halogens
what are the physical properties of group VII halogens?
exist as diatomic atoms
low melting and boiling point
coloured substances
what are the chemical properties of group VII halogens?
halogens can undergo displacement reactions. a more reactive halogen can displace a less reactive halogen from its salt solution.
powerful oxidising agents
what are the trends down group VII halogens?
melting and boiling point increases
reactivity decreases
colour intensity increases
solidity increases
electrons shells increase
why do the electron shells increase down group VII?
as the distance between the valence shell and the nucleus increases, the attraction force decreases. hence, it is less likely to gain one valence electron and reactivity decreases
what are group 0 elements?
group 0 are called noble gases and they have a stable configuration
