1. Structure of an atom and the Atomic timeline

2. Review What is an element made up of? Two or more elements Element
Compound
What is an element made up of?
In our previous block, we learnt about elements. Can someone define for me what do we mean by an element? Give me an example.
An element is a pure substance that cannot be separated further into a simpler substance by physical or chemical means. Example is gold, lead or copper. In other words, an element is made up of similar atoms.

3. Today we will learn… That an element is made up of atoms
Parts of an atom
How the atom was discovered – atomic timeline

4. What is an atom?
An atom is the smallest particle into which an element can be divided and still be the same substance.
rkm.com.au

5. Atoms are building blocks of matter because…
element 1
element 2
Compound
MATTER
Atom 2
Atom 1
Atoms make up elements
Elements make up compounds
Elements and compounds make up matter.

6. Parts of an atom
Nucleus is the small, dense, positively charged center of the atom.
Protons are positively charged particles in the nucleus.
Neutrons are particles in the nucleus of an atom that have no charge.
Electrons are negatively charged particles found in electron clouds outside the nucleus.

7. Let’s compare the parts of the atom
Charge
Mass
Location
Proton
Positive
1 amu
Nucleus
Neutron
No charge/
Neutral
Electron
Negative
Almost zero
Electron clouds (external to nucleus)
1 atomic mass unit (amu) = 1.7 X g

8. Properties of an atom
Most of the atomic mass is present in the nucleus because the mass of the electron is almost equal to zero.
Mass of a proton = mass of a neutron= 1a.m.u
The atom has no charge (neutral) because number of protons = number of electrons.

9. There is something even smaller than protons and neutrons…
Quarks are smaller particles that make up protons and neutrons.

10. Quick review Which of these is NOT one of the basic pieces of an atom?
Electron
Proton
Quantron
Neutron

11. Quick review
If I ask you to draw a nitrogen atom, what would you show in the nucleus of the atom?
Molecules
Neutrons
Protons
Electrons

12. Story of the atom Also known as the Atomic Timeline 440 BC 1803 1911
1897
1913
20th century

13. Democritus 440 BC Proposed the “atom” Atoms are small, hard particles
constantly move
are “uncuttable”
440 BC
1803
1911
1897
1913
20th century

14. John Dalton 1803 Conducted experiments in combining elements
All substances are made up
of atoms
Atoms of the same element are exactly alike
Atoms of different elements are different
Elements combine in specific proportions
440 BC
1803
1911
1897
1913
20th century

15. J. J. Thomson 1897 Conducted the cathode ray tube experiment
There are small, negatively
charged particles inside the atom
“Plum pudding” model
440 BC
1803
1911
1897
1913
20th century

16. E. Rutherford 1911 Gold foil experiment Atoms contain mostly empty
space
Small, dense positively charged nucleus
Most of the atom’s mass is in the nucleus
Electrons move around in empty space in the atom
440 BC
1803
1911
1897
1913
20th century

17. N. Bohr 1913 Electrons travel in definite paths
Electrons jump between levels
from path to path
440 BC
1803
1911
1897
1913
20th century

18. Schrödinger and Heisenberg 20th century
Electron paths cannot be
predicted
Electrons are found in electron
clouds, not paths
440 BC
1803
1911
1897
1913
20th century

19. Quick Review
How is the modern model of an atom different from the Bohr atomic model?
The masses of the atomic particles are different.
The numbers of electrons are different.
The shapes of the nuclei are different.
The arrangements of the electrons are different.

20. Atomic Timeline worksheet
Complete this in class. If it is not done in class then it will become a homework?

21. Wrapping up What we learned today Homework Next time What is an atom?
Parts of an atom
Atomic timeline
Homework
Timeline?
Next time
Continue with more information about the atom
Learn about how atoms help elements find their spot on the Periodic Table
I’m positive!
I’m negative!
I could care less!