The Periodic Table Flashcards
What did scientists discover about the periodic table?
scientists discovered that matter is made up of substances we call elements
What is an element made up of?
1 atom
Who created the first periodic table?
Dimitri Mendeleev
How did he arrange the elements?
he arranged the elements in order of increasing atomic mass into columns.
what is the difference between the periodic table then vs modern time?
the modern periodic table is organized according to atomic number (which is the number of protons in an atom) rather than atomic masses.
Why is the periodic table important?
the table acknowledges the existence and properties of all elements.
Elements are composed of:
only one type of atom
atoms exist individually or in compounds (molecules)
cannot be broken down or separated by physically or chemically changes
compounds:
can be broken down into tow or more elements by chemical changes but not by physical.
Mixtures:
can be separated into parts by physical changes
Why do chemists use chemical symbols?
because elements have different names in different languages
What are all elements represented by?
symbols
What do chemical symbols consists of?
one or two letters
Describe a chemical symbol:
A
B
C
D
A: some elements have a chemical symbol with just one letter (first letter of name) ex Hydrogen H.
B: for some elements the symbol comes from another language. ex. Potassium- K
C Some elements have a chemical symbol with 2 letter ex. Silicon Si
D other times the second letter is from another part of the word. Magnesium- Mg
What is a period
the set of all elements in a given row across the table.
they have the same number of electron shells
What is a group/family?
the set of all the elements in a given column going down the table.
they have the same number of electrons on the outermost shell.
