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atomic structure and the periodic table - Coggle Diagram
atomic structure and the periodic table
atomic structure
compounds: compounds are substances formed from two or more elements and held together by a chemical bond
difficult to seperate original elements of. compound out again and a chemical reaction is used to do this
a compound formed from non-metals consists of molocules. each atom shares an electron with another Aton. this is called covalent bonding. examples: carbon monoxide and water
a compound which is formed from a metal and a non-metal consists of ions. the metal atoms lose electrons to form positive ions and the non-metal atoms gain eletrons to form negative ions. because they are opposite charges they ar strongly attached to each other. this is called ionic bonding
isotopes: have same atomic number but different mass numbers
mixtures: there is no chemical bond they can be seperated out by physical methods such as filtration or crystallisation
electronic structure: 1st shell 2 electrons 2nd shell 8 3rd shell 8.
history of the atom:
at the start of the 19th century John dalton described atoms as solid spheres and said that different spheres made up different elements.
in 1897, jj thomson concluded that atoms were not solid spheres. he showed that an atom must contain even smaller, negatively charged particles-electrons
the solid sphere idea of atomic structure had to be changed. the new theory was known as the plum pudding model.
this showed the atom as a ball as a positive charge with electrons stuck in it
the periodic table
the modern periodic table
in the periodic table the elements are laid out in order of increasing atomic number. each group tells you how may electrons in the outer shell. for example group one elements have one electron in the outer shell
devopment of the periodic table:
in the early 1800 elements were arranged by. there atomic mass
mandeleev left gaps in the periodic table and predicted new elements. he placed the elements mainly in order of atomic mass. he would switch the order if the properties meant it should be changed. for example iodine has a smaller relative atomic mass but placed after tellurium as it has similar properties to the elements in hat group
metals and non metals
metals are elements which can form positive ions when they react. non metals don't generally form positive ions when they react
for non metals forming positive ion is much more difficult. this is because they have lots of electrons to remove to get a full outer shell. close to nucleaus to feel a strong reaction
metals to the left of the periodic table don't have may electrons to remove and metals towards the bottom of the periodic table have outer electrons which
group 1 metals
all soft and have low density. all have 1 electron in their outer shell
trends: increasing reactivity. higher relative atomic mass and lower melting points and boiling pionts
alkali form ionic compounds with non-metals. group 1 elements