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Science 8th grade - Ch 4-2 other
By 1869 how many elements had been discovered?
Dmitri Mendeleev discovered a set of __________ applied to all the elements.
How did Mendeleev arrange the elements?
in order of increasing atomic mass
What is atomic mass?
the average mass of all the isotopes of an element
In 1869 _________ published the first periodic table with ______ elements and three missing elements?
What are the two differences between Mendeleev's table and the modern periodic table?
(1) new elements have been added as they were discovered (2) arranged in order of atomic number , NOT atomic mass
Who discovered a way to measure the positive charge ( the atomic number) on an atom's nucleus?
Henry Moseley in 1913
The properties of an element can be predicted from its location in the __________ _______
The _________ of an element can be predicted from its location in the periodic table
The horizontal rows are called _________
From left to right, the properties of elements in a period change in a _________
From left to right the _________- of elements in a period change in a pattern
The verticals columns are called _________
What are groups in the periodic table sometimes called?
THe elements in the same group have ________ characteristics
What are the four things (from top to bottom) that are included in each square for an element?
(1)atomic number (number of protons), (2) chemical symbol (3) name (4) atomic mass
WHere do the elements come from?
Like many stars, the sun is made of mostly which element?
The hydrogen is at high pressure and extremely high temperatures and it's state of matter is _______
What is plasma?
a state of matter that is gas-like and is made of free electrons and nuclei of atoms without electrons
When these nuclei in the plasma collide they join together and form larger nuclei and release huge amounts of ___________
What is nuclear fusion?
when smaller nuclei combine and form larger nuclei - in stars
In the sun when isotopes of hydrogen fuse they make nuclei of ______
What is the most important source of energy in the sun?
When hydrogen fuses to form helium nuclei and energy is produced
Helium builds up in the sun's core and one or two helium nuclei fuse and form _________
WHen a helium nucleus fuses with a beryllium nucleus what is formed?
Fusion keeps going until the core of the star is almost all _________
What do we call it when a star explodes?
A supernova provides enough energy to create the ________ ____________
What happens to the heavy elements that a supernove creates?
they are blown of into space as the star burns out
THe matter in the sun and its planets originally came from a gigantic _________