Chapter 4 Section 1: Introduction to atoms Key Concepts: Proton How did atomic theory develop and change? Energy level Neutron What is the modern model of the atom? Atomic number Key terms: Isotope Atom Mass number Electron Nucleus

Atoms and atomic theory Atoms (as you know) are the smallest particles of elements Atomic theory grew as a series of models (models- you know them from chapter 1) that developed from experimental evidence. As more evidence was collected, the theory was revised.

Everything… is made of atoms. (not on the test… If you made a tiny dot with the tip of a sharp pencil, and the pencil lead were made of carbon, the tiny dot would have about 4 billion billion carbon atoms.”

John Dalton English chemist. Proposed an atomic theory and model for atoms. With only a few changes, the theory is still widely accepted. “my spectacles are the bomb foshizzle”

All elements are composed of atoms that cannot be divided Dalton’s theory (yes, you need to know it, because it is true and it will help you understand atoms) All elements are composed of atoms that cannot be divided All atoms of the same element are exactly alike and have the same mass. Atoms of different elements are different and have different masses. An atom of one element can’t be changed into another. Every compound is composed of atoms of different elements, combined in a specific ratio.

So true.

Smaller parts of atoms Scientists realized that atoms are composed of even smaller parts. 1897, JJ Thompson found that atoms contain negatively charged parts (they later became known as electrons) 1911 – Ernest Rutherford found the nucleus and protons (you will not be tested on this, this is background info – you should know it, tho )

Evolving models Scientists created better and better models of atoms as they got new information. (this you should know) 1913 – Niels Bohr revised it again. He showed that electrons could only have specific amounts of energy, leading them to move in certain orbits (this is just background info)

Structure of atoms as we know it today Nucleus – the tiny, positively charged, center of an atom. It contains protons and neutrons. Protons – positively charged particles inside the center (+) Electrons – negatively charged particles (form a cloud-like region around the nucleus) (-) Neutrons – electrically neutral particles inside the center (no charge)

Atoms Have an equal number of positively charged protons and negatively charged electrons. Hence (heh, hence), they USUALLY have no charge.

http://www.youtube.com/watch?v=QbWKF9uDF7w

The electron cloud The “cloud” is a visual model. It symbolizes where electrons are likely to be found. They’re moving all the time within this region. An electron’s movement is related to its energy level, or the specific amount of energy it has.

Particle masses and size of atoms It takes almost 2000 electrons to equal the mass of just one proton. Together, protons and neutrons make up nearly all the mass of an atom. Protons and neutrons have about the same mass. Atoms are… small. A tiny speck of dust may contain 10 million billion atoms. No, that’s not a made up number like “Oh yeah? I’m 10 million billion times sure I’m right…”

Atomic number Every atom of an element has the same number of protons. Example: every carbon atom has 6 protons. Every oxygen atom has 8 protons. This number of protons is called the atomic number.

Isotopes and mass number Atoms with the same number of protons and a different number of neutrons are called isotopes. All atoms of an element have the same number of PROTONS, but neutron number can vary. Examples: Carbon 13 has 7 neutrons, carbon 14 has 8 neutrons. Isotopes are identified by mass number, which is the sum of protons and neutrons. Some isotopes are more common than others: Carbon 12 is more common than 13 or 14.

OMG What should I know?? OMG KNOW IT ALL! I will help you  start by learning what I ask you in the review questions… If you are confused, use the book to review. Reading the chapter, regularly, will help you retain information. At any point, if you have questions, are unsure, want to improve your test grades, ask me. I am here to help you. Email me. If you don’t have email, I will give you my digits bruh.

Review questions What is atomic number? What is an isotope? Where do you find electrons, neutrons, and protons? (specifically) How are atom parts (electrons, neutrons, protons) charged? Draw an atom and label its parts What are the four parts of Dalton’s theory? THIS IS WHAT I WILL ASK YOU ON THE ASSESSMENT TOMORROW. KNOW IT KNOW IT KNOW IT KNOW IT KNOW IT! STUDY THESE THINGS TONIGHT! WHILE YOU ARE BRUSHING YOUR TEETH! WHILE YOU ARE INSTAGRAMING!