The person who developed the first periodic table of elements.
Who is Dmitri Mendelev?
100
On the first periodic table, from left to right across each row, elements are arranged by ___________.
What is increasing atomic mass?
100
The columns on the periodic table are known as _________.
What are groups?
100
The table of the elements is called a periodic table because of its ________________.
What is repeating pattern?
100
In the periodic table, the rows are known as __________.
What are periods?
200
An important measure of a good __________ is its ability to make accurate predictions.
What is a model?
200
In the modern periodic table, elements are organized by____________.
What is atomic number?
200
The atomic number is the number of _________ in an atom of an element.
What is protons?
200
In the modern periodic table, __________ increases from left to right across each period, and it also increases from top to bottom within each group.
What is atomic number?
200
Besides atomic number, the periodic table includes each element's ___________ and __________.
What are chemical symbol and class?
300
Name 3 classes of elements.
What are metals, metalloids, and nonmetals?
300
From left to right across a period, each element has one more __________ than the element before it.
What is a proton?
300
_____________ in the same group have similar properties.
What are elements?
300
Elements that are good conductors of electricity.
What are metals?
300
Elements that do not conduct electricity.
What are nonmetals?
400
Elements that fall between metals and nonmetals in the periodic table.
What are metalloids?
400
The increase in ____________ across the periodic table explains why elements go from nonmetals to metalloids and then to metals from left to right across the table.
What is protons?
400
The electrons in the outer energy level of an atom are called ___________ electrons.
What is valence?
400
_____________ determines an element's reactivity and whether the element can conduct an electric current.
What is the number of valence electrons?
400
Elements in the same column or group of the periodic table have the same number of ___________ in their outer energy level.
What are valence electrons?
500
In group 1 of the periodic table, all of the elements except ________ are ___________ metals.
What is hydrogen and alkali?
500
Transition metals are all ___________ metals.
What is radioactive?
500
Groups 13-16 contain what two groups.
What are nonmetals and other metals?
500
The halogens react violently with _____________, which have one valence electron.
What is alkali metals?
500
Group 18 elements are nonmetals called _____________.