elements and periodic table Flashcards
what is a pure substance in called in chemistry
substance
what can be a pure substance
an element or compound
what is a pure substance
one that has the same composition and properties throughout
what are elements
substances made up of one type of atom
who used a chemical symbol to represent elements
swedish scientist jon berzelius
what are chemical symbols derived from
the first and maybe second letter of its latin name
how many elements occur naturally
90
how many elements have been created or synthesized by humans
19
who created the periodic table
dmitri mendelev
what does the atomic number represent
the amount of protons in an atom
where are the lanthanide and actinide series located
bottom of the periodic table
what is each entry in the periodic table called
a tile
what are the horizontal rows in the periodic table called
periods
what are the vertical columns in the periodic called
families or groups
do elements in a group have different properties
no
do elements in a period have different properties
yes
which group is the halogen
VII A
where are metals found
on the far left of the periodic table
where are metalloids
in the middlish
where are non-metals found
on the far right
what does the reactivity of an element depend on
the number of valence electrons
what are valence electrons
the number of electrons found in the outermost energy level of an atom
the group numbers in a periodic table are equal to what
the number of valence electrons
what is the atomic mass of an element equal to
the number of protons plus neutrons
what are isotypes
atoms of the same element that have different numbers of nuetrons
what happens in a neutral atoms
the number of protons is equal to the number of electrons
atoms are usually what
nuetral
