Comprehensive Chemistry Unit 3: Atomic Theory, Experiments, and Periodicity

What is Dalton's first atomic theory?

All matter is made of atoms.

What is Dalton's second atomic theory?

All atoms of the same element are alike.

What is Dalton's third atomic theory?

Atoms combine at fixed ratios to form compounds.

What is Dalton's fourth atomic theory?

Atoms can combine at different ratios to form different compounds.

What is Dalton's fifth atomic theory?

Atoms are neither created nor destroyed in a chemical reaction.

What is observation in science?

Observation is 5 sense data about the world and is limited when we are unable to sense the object of our observation.

What is the difference between microscopic and macroscopic?

Micro - small; macro - big.

What does the Gold Foil Experiment conclude?

The gold atoms are mostly empty and have a dense, positive nucleus.

What does the Cathode Ray Experiment demonstrate?

The beam, which is made of electrons, is negatively charged.

What does the Oil Drop Experiment allow scientists to calculate?

The mass and charge of the electron.

How did Mendeleev organize the elements?

According to their properties.

What do the blank spaces in period 5 of Mendeleev's table represent?

Elements which had not yet been discovered.

What do the formulas in the title block of each group represent?

The types of compounds the element makes.

Why is Mendeleev's periodic table considered a good model?

It allowed him to predict undiscovered elements.

What is atomic radius (AR)?

The relative size of the atom.

How does atomic radius change across a period?

AR increases from left to right.

How does atomic radius change within a group?

AR increases from top to bottom.

What is electron affinity (EA)?

The measure of how much an atom attracts electrons.

How does electron affinity change across a period?

EA increases from left to right.

How does electron affinity change within a group?

EA increases from top to bottom.

What is ionization energy (IE)?

The amount of energy required to remove an electron from an atom.

How does ionization energy change across a period?

IE decreases from left to right.

How does ionization energy change within a group?

IE decreases from top to bottom.

What is an ion?

An atom that has gained or lost electrons.

What is an isotope?

Any atom of the same element with a different number of neutrons.

What is mass number?

The sum of the number of protons and neutrons in an atom.

What charge does sodium (Na) have after losing 1 electron?

+1

What charge does sulfur (S) have after gaining 2 electrons?

-2