QOTD 10/21/13

1. HW check: Please get out the homework from Friday (p. 53-58)

2. QOTD: Do the chem catalyst on page 59

ANSWERS to Lesson 1.3.2 Activity Questions

1. Label the electrons, nucleus, neutrons, and protons in the pictures above.

Electrons Nucleus Protons (white)

Neutrons (black)

2. Each atom is neutral. Explain why.

There is always an equal number of electrons (negatively charged) and protons (positively charged)

Example: 4 protons and 4 electrons

3. How did you know which were the protons and which were the neutrons?

# e- = # p+ Number of electrons is the same as number of protons.

Usually # n0 > # p+ we will see why when we study radioactivity

4. Is the nucleus of these atoms positive, negative, or neutral? Explain your reasoning.

The nucleus is positive because it only contains protons (positively charged) and neutrons (no charge).

5. Use a periodic table to fill in table 1.3.2 on the following page.

See the PDF file

6. How did you figure out the number of electrons in each atom?

As long as we assume the atom is neutral (no overall charge), the number of electrons is equal to the # of protons.

Note that it is possible to add or remove electrons from an atom and thus make the atom have a + or – charge! We call these ions

7. How did you figure out the number of protons in each atom?

It’s ALWAYS the same as the atomic number.

8. How did you figure out the number of neutrons in each atom?

You take the mass number and subtract the number of protons.

9. How does the mass number of each atom compare to the atomic weight given on the periodic table?

It’s the rounded whole number of the atomic weight.

10. Make a drawing of a nitrogen atom, similar to those given for beryllium, fluorine, and carbon.

7 protons, 7 neutrons, 7 electrons

Chem catlyst page 59 (QOTD)

• What is different? – The one on the right has one more neutron

• What are the atomic numbers?– Both are 3

• What are the mass numbers?– Left: 6 right: 7

• Do you think they are both lithium?– Yes! Both have 3 protons

Today’s Learning Target

• You should be able to:– Describe what an isotope is and write isotope

symbols– Determine what isotope is most prevalent for a

given element

Note Time!

• Find a spot in your notebook for some notes. • Title it “isotope notes” or something like that• Don’t forget to put it in your TOC!

Isotopes

• Isotopes – atoms of the same element but with different mass numbers

• Same number of protons

• Different numbers of neutrons

Atomic mass

• Atomic mass – the mass of a single atom• Measured in unified atomic mass units (u)• 1 u is defined as exactly 1/12th of an atom of carbon-12• 1 proton = 1 u 1 neutron = 1 u• 1 u is TINY : 1 u = 1.66 x 10-24 g• Or 6.02 x 1023 u = 1 g – you WILL memorize this number later. It is called the “mole”

Isotope Names and Symbols

• We name isotopes by their mass number• Ex: carbon-14

• We can write this in shortand using symbols

• Ex: 14Csuperscript = mass number

Subscript = atomic number

6

Practice

• How many protons does helium-3 have?• How many neutrons?• What is the mass number?• What is the chemical symbol for helium?• Write the chemical symbol for the helium-3

isotope

Assignment/HW

• Complete p. 60-64• Skip “if you finish early” on page 61• Skip Qs 7 and 8 on p. 64