Flashcards in Chapter Two Deck (36):
Who was Dmitri Mendeleev and what did he do?
he was a Russian chemist who sorted the first 63 elements into data card in oder of their atomic mass and other properties of the element and its compounds. He proposed the first systematic order for elements
What was so revelational about Mendeleev's way of ordering the elements?
He arranged them in groups according to their similar chemical properties and ordered them in increasing order of relative atomic mass and the periodicity of their properties. He even left room for the undiscovered elements
What did Mendeleev first propose?
He proposed the first periodic law relative to atomic masses, mean they were arranged I incasing atomic mss, similar physical and chemical properties occurring at regular intervals
How did Mendeleev order the elements?
He ordered them in vertical groups going across all with similar physical and chemical properties and in horizontal rows I increasing atomic mass
What does the atomic number relate to?
The number of protons in a nucleus of an atom of that element
What are the four main principles that the periodic table arose from?
1- atomic number, rather than mass
2-repaeting patterns of electron configuration were observed and are now ordered in increasing energy levels
3- arrangment of the outer-shell electrons was most important in determining the chemical properties of an element
4- the periodic recurrence of similar properties was seen to result from the periodic change in the electric structure
What do the periods correspond with?
the 7 periods correspond to the filling of a shell
What are the elements in group 1&2?
highly reactive metals and are know as the s block
What are the elements in group 13-18?
the p block
What are the elements in group 3-12?
transition metals/transition elements and are know as d-block elements
Why is helium a retard?
as its a group 2 element with a filled s sub-shell of innermost K shell of an atom, making it un-reactive so is grouped with the nobles gases as it show similar properties
What are the elements the lanthanoids and actinoids?
inner transition elements and progressively fill the f subshell
Where are no-metals found?
towards the right side
Where are the metals found?
towards the left side
What properties do the transition elements have, how reactive are they, what do they form?
they have the properties of metals but are less reactive than s block metals and most form coloured compounds and most can form ions
What does atomic size generally do going down a group on the periodic table, why?
increase as more electrons are added to successively higher energy levels which is further out from the nucleus, thus increasing size
What happens to the positive charges as you go down a group, what happens to the nuclear charge?
increases and the nuclear charge (attraction of positive charges on the nucleus to the electrons) increases
What do the inner electrons create and do?
the create a shielding effect thereby decreasing the pull of the nucleus on the outermost electrons
What happens to atomic size from left to right across a period?
decreases as each atom maintains the same number of main shells and as you go down another proton and electron is added to the same shell so the effect of the increasing nuclear chore on the outermost electrons is to pull them closer to the nucleus thus decreasing in size
How do elements form ions?
they gain or lose electrons
What is energy is required to make ions?
ionisation engird is required to remove an electron from an atom
When moving down a group what happens to the size of an atom?
the size increases as the outermost electrons are further from the nucleus. The nucleus therefore does not hold these electrons as strongly as they are more easily removed. there for the atom has a lower is ionisation energy
What is electronegativity?
electronegativity is defined as the ability of an element to gain electrons when bonding
How is electronegativity expressed?
in arbitrary units on the Pauling electronegativity scale
Going left to right on the main-group elements what happens to their electronegativity?
it increases as, the nuclear charge in creases by one unit, as one electron is added to the outer shell. As the positive charge in the nucleus increases, the atom has an increasing electron-attracting power and therefor increasing electronegativity
What happens moving down a group to the electronegativity?
the electronegativity decreases as the outer electrons are further away from the nucleus and the shielding effect deceases the electron-attracting power of the atom
What are metallic characteristics determined by?
an elements ease to lose electrons
As elements move across the a period, what happens?
they lose their metallic characteristics as, the number of electrons in the same shell increases across a period and the nuclear charge also increases the electrons become less easily lost from positive ions.
As elements move down a group, what happens?
they become more metallic as the outer shell electrons are further away from the nucleus because of increased number of shells and are less strongly attracted
What is oxidising strength?
how readily an element gains electrons
What are elements gain electrons easily strong in?
they are strong oxidants and are themselves reduced
What is the reducing strength of an element defined as?
how readily an element loses electrons
What makes a stronger reductant?
the more readily an element gives up electrons the more easily it is oxide making it a stronger reductant
What happens when moving across a period in relation to reducing strength?
the reducing strength decreases as, the atoms give up their outer shell electrons less readily, and the oxidising strength of these elements increases as elements gain electrons more readily
List the general properties of metals
-high melting/boiling points
-good conductors of heat and electricity
-shiny/ lustrous appearance
-ductile and malleable
-form positive ions