Structure of an atom and the Atomic timeline

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.

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

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

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.

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. http://www.chem4kids.com/files/atom_structure.html

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 10-24 g

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. http://www.chem4kids.com/files/atom_structure.html

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

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

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

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

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

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

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

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

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

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

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.

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

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!