Chapter 1 St: Atoms Flashcards
What is an Atom?
It is the smallest particle of matter. It cannot be chemically divided.
Why have scientists devised various models to represent atoms?
Because atoms are too small to be examined directly.
What is Dalton’s “Billiard Ball” model?
He discovered that atoms are the smallest solid units of matter and that atoms are solid and divisible.
What is J.J Thompson’s model?
He suggested the “Plum Pudding” model of the atom and that negative charges distributed in a positive sphere.
Why did Thompson show when referring to the “rays”? What did this indicate? What did he add?
He showed that the rays could be bent by nearby electric charges. This indicated that they were tiny negatively charges particles. He called them electrons. Thompson adds negatively charged electrons as part of an atom.
What did Ernest Rutherford bombard?
He bombarded a thin Au foil with alpha particles (positively charged)
Describe Rutherford’s “ray” results and conclusions.
1- result: went straight through. Conclusion: means atom is mostly empty space.
2- result: 1/1000 was deflected. Conclusion: means nucleus was positive and that the nucleus is very small.
3- result: 1/100 000 bounced back. Conclusion: means that nucleus is approximately 100 000 times smaller than the atom and the nucleus is very dense.
Describe the Bohr Rutherford Atomic model
Proposed that electrons moved in energy levels and that the ones in the outermost orbit determined the chemical properties of that atom
What does the Bohr Rutherford model contain (2)
Small positive nucleus (protons)
Surrounded by negatively charged electrons that move in defined orbits
What did James Chadwick add?
Adds the neutron in nucleus
Describe what a neutron is
One of the particles that make up an atom. With the proton, it forms the nucleus. It has no charge and is neutral.
What is an electron
One of the particles that make up an atom and it is negatively charged
What is a proton
One of the particles that make up an atom. It is found in the nucleus and carries a positive change.
What is the symbol for the electron, proton, and neutron?
Electron = e-
Proton = p+
Neutron = n0
Describe the simplified atomic model
Protons and neutrons in nucleus
Surrounded by a number of electrons in each energy shell.
Finish the sentences.
Number of protons=
Number of electrons=
Atomic number
Number of protons.
How does one find the # of neutrons?
Atomic mass-Atomic number= # of neutrons
Where is the atomic mass located?
Underneath the element
Where is the atomic number located?
On top of the element
Describe the Energy Level: Octet Rule
For the first 20 elements, the orbitals are 2-8-8-18
What must happen to orbits
They must be filled before starting a new one
What are valence electrons?
They are the electrons in the outer most shell of an atom.
What is the Lewis dot representation?
It is a simplified representation that shows the symbol of the element and only illustrates the valence electrons.
What is a group?
-A column of the periodic table.
-elements in a group have similar chemical properties as they have the same amount of valence electrons.
