Elements and Subatomic Particles Notes

Elements and Subatomic Particles

  • The world is composed of atoms that bond to form compounds.
  • Elements are distinct types of atoms.
  • Elements differ based on their subatomic structure (protons, neutrons, electrons).
  • The number of protons determines the element's identity; this is the atomic number.
  • Each element has a unique atomic number.
  • Elements exist with varying numbers of protons, some being more common.
  • Atoms typically have an equal number of protons and electrons, with a similar number of neutrons.

Atomic Structure

  • In the 1800s, it was discovered that atoms contain positive and negative charges.
  • The arrangement of these charges within the atom was initially unclear.
  • The prevalent model was a loosely positive sphere with pockets of negativity.

Gold Foil Experiment

  • In 1911, Rutherford conducted an experiment, directing positive alpha particles at a thin gold strip.
  • The expectation was that alpha particles would pass through undeflected, assuming the positive charge was dispersed.
  • The results showed that most alpha particles passed through without deflection, but some deflected sharply.
  • This indicated that the atom is mostly empty space, with the positive charge concentrated in small, dense areas.
  • The experiment revealed that positively charged protons reside in a densely packed nucleus.
  • Negatively charged electrons exist outside the nucleus and have significantly less mass than protons.

Mass Number

  • Protons repel each other within the nucleus.
  • Neutrons stabilize the nucleus by 'gluing' protons together via a strong force.
  • Neutrons are neutral in charge and have approximately the same mass as protons.
  • The mass number is the sum of protons and neutrons in an atom.
    • Electrons are not considered in the mass number due to their negligible mass.

Isotopes

  • Isotopes are variations of an element with different numbers of neutrons, leading to different masses.
  • Isotopes of an element share the same number of protons.
  • Isotopes generally possess similar chemical properties due to the neutral charge of neutrons.
  • Neutrons usually do not influence bonding behavior.
  • Isotopes exhibit different physical properties due to their varying masses.
  • Some isotopes are radioactive.

Examples of Isotopes

Carbon-12

  • Protons: 6
  • Electrons: 6
  • Mass: 12
  • Neutrons: 6
  • Most common type of carbon.

Carbon-13

  • Protons: 6
  • Electrons: 6
  • Mass: 13
  • Neutrons: 7
  • Rare isotope of carbon.

Carbon-14

  • Protons: 6
  • Electrons: 6
  • Mass: 14
  • Neutrons: 8
  • Used in carbon dating of artifacts 5000+ years old.

Chlorine-35

  • Protons: 17
  • Electrons: 17
  • Mass: 35
  • Neutrons: 18
  • About 75% of chlorine atoms.

Chlorine-37

  • Protons: 17
  • Electrons: 17
  • Mass: 37
  • Neutrons: 20
  • About 25% of chlorine atoms.

Elements and Subatomic Particles Worksheet

  • This section seems to present a worksheet with a table to be filled using the periodic table. The table requires filling in the proton number, electron number, neutron number, and mass number for various elements given their symbol.

  • Hydrogen

    • Symbol: H
    • Proton #: 1
    • Electron #: 1
    • Neutron #: 0
    • Mass #: 1

  • Lithium

    • Symbol: Li
    • Proton #: 3
    • Electron #: 3
    • Neutron #: 4
    • Mass #: 7

  • Beryllium

    • Symbol: Be
    • Proton #: 4
    • Electron #: 4
    • Neutron #: 5
    • Mass #: 9

  • Carbon

    • Symbol: C
    • Proton #: 6
    • Electron #: 6
    • Neutron #: 6
    • Mass #: 12

  • Oxygen

    • Symbol: O
    • Proton #: 8
    • Electron #: 8
    • Neutron #: 8
    • Mass #: 16

  • Fluorine

    • Symbol: F
    • Proton #: 9
    • Electron #: 9
    • Neutron #: 10
    • Mass #: 19

  • Neon

    • Symbol: Ne
    • Proton #: 10
    • Electron #: 10
    • Neutron #: 10
    • Mass #: 20

  • Magnesium

    • Symbol: Mg
    • Proton #: 12
    • Electron #: 12
    • Neutron #: 13
    • Mass #: 25

  • Aluminum

    • Symbol: Al
    • Proton #: 13
    • Electron #: 13
    • Neutron #: 14
    • Mass #: 27

  • Silicon

    • Symbol: Si
    • Proton #: 14
    • Electron #: 14
    • Neutron #: 14
    • Mass #: 28

  • Phosphorus

    • Symbol: P
    • Proton #: 15
    • Electron #: 15
    • Neutron #: 16
    • Mass #: 31

  • Sulfur

    • Symbol: S
    • Proton #: 16
    • Electron #: 16
    • Neutron #: 18
    • Mass #: 34

  • Chlorine

    • Symbol: Cl
    • Proton #: 17
    • Electron #: 17
    • Neutron #: 18
    • Mass #: 35

  • Argon

    • Symbol: Ar
    • Proton #: 18
    • Electron #: 18
    • Neutron #: 22
    • Mass #: 40

  • Potassium

    • Symbol: K
    • Proton #: 19
    • Electron #: 19
    • Neutron #: 20
    • Mass #: 39

  • Calcium

    • Symbol: Ca
    • Proton #: 20
    • Electron #: 20
    • Neutron #: 20
    • Mass #: 40

  • Mercury

    • Symbol: Hg
    • Proton #: 80
    • Electron #: 80
    • Neutron #: 120
    • Mass #: 200

Multiple Choice Questions

  • Which of the following is not in the nucleus?
    • A. Electrons
    • B. Neutrons
    • C. Protons
    • D. They are all in the nucleus
    • Correct Answer: A. Electrons
  • Which of the following subatomic particles has the least mass?
    • A. Electrons
    • B. Neutrons
    • C. Protons
    • D. They are all about the same mass.
    • Correct Answer: A. Electrons
  • Which of the following subatomic particles is not charged?
    • A. Electrons
    • B. Neutrons
    • C. Protons
    • D. They are all charged.
    • Correct Answer: B. Neutrons

Open Ended Questions

  • How many neutrons are present in sodium – 23?
    • A. 11
    • B. 12
    • C. 23
    • D. 34
    • Correct Answer: B. 12 (Since Sodium has 11 protons and mass number is 23. Therefore 23-11 = 12)
  • Boron has two main isotopes, one with five neutrons and one with six neutrons.
    • a. State the number of protons in each isotope.
      • Boron has 5 protons in each isotope because the number of protons defines the element.
    • b. State the mass number in each isotope.
      • For the isotope with 5 neutrons: 5 (protons) + 5 (neutrons) = 10. Mass number is 10.
      • For the isotope with 6 neutrons: 5 (protons) + 6 (neutrons) = 11. Mass number is 11.
  • This question is about neutrons.
    • a. What is the function of neutrons in the nucleus?
      • Neutrons stabilize the nucleus by mediating the repulsive forces between protons.
    • b. Why do hydrogen atoms typically have zero neutrons?
      • The most common isotope of hydrogen, Protium, has only one proton and no neutrons. Since there's only one proton, no neutrons are needed for stabilization.
  • Why was the correct model of the atom so hard to hypothesize before 1911?
    • Before Rutherford's gold foil experiment, the distribution of positive and negative charges within the atom was unknown. The plum pudding model was a popular hypothesis, which suggested a uniformly distributed positive charge with electrons scattered throughout. This made it difficult to conceive of a concentrated, positively charged nucleus.
  • Why would the idea of a nucleus be laughed at by 19th-century scientists?
    • The idea of a nucleus, with all the positive charge concentrated in a tiny space, would have been counterintuitive to 19th-century scientists because it implied an extremely high charge density. It was believed that positive charge was spread out.