1.5 Size and mass of atoms

• Atoms with a higher atomic number are generally larger in size


  True
• What is atomic mass approximately equal to?

  Protons + neutrons
• What happens to atomic size as you move across a period from left to right?

  It decreases
• Order the following elements by increasing atomic size across a period:

  1️⃣ Carbon

  2️⃣ Boron

  3️⃣ Beryllium

  4️⃣ Lithium
• The shielding effect increases atomic size as you move down a group


  True
• Atomic mass units are often abbreviated as amu
• Atomic mass refers to the total mass of protons and neutrons in the nucleus
• As atomic number increases across a period, the greater number of protons pulls the electrons closer
• The shielding effect from inner shells reduces the attractive force on outer electrons
• The size of an atom is affected by its atomic number, electron shells, and the shielding
• Atomic mass is often expressed in atomic mass units or unified atomic mass units
• Match the element with its atomic number and atomic mass:

  Hydrogen ↔️ 1 and 1.008

  Carbon ↔️ 6 and 12.011

  Nitrogen ↔️ 7 and 14.007

  Oxygen ↔️ 8 and 15.999
• The shielding effect remains constant as you move across a period


  True
• As you move down a group, the number of electron shells increases, leading to a larger atomic size.
• What is the approximate atomic mass of an atom equal to?

  Number of protons + neutrons
• Why do different isotopes of the same element have different atomic masses?

  They have varying neutrons
• Atomic size decreases as you move from left to right across a period in the periodic table.

  True
• What is the primary reason atomic size increases as you move down a group in the periodic table?

  Increasing electron shells
• What corresponds to the number of protons in an atom's nucleus?

  Atomic number
• Arrange the following elements in order of increasing atomic mass: Lithium, Sodium, Potassium, Rubidium, Cesium

  1️⃣ Lithium

  2️⃣ Sodium

  3️⃣ Potassium

  4️⃣ Rubidium

  5️⃣ Cesium
• What does atomic size refer to?

  Diameter of an atom
• Match the factor with its effect on atomic size:

  Atomic Number ↔️ Higher atomic number = larger atom

  Atomic Shells ↔️ More shells = larger atom

  Shielding Effect ↔️ Reduces overall atomic size
• The atomic number of an atom is equal to the number of protons


  True
• As you move across a period, the increasing atomic number leads to more protons, which shrinks the atom.
• What happens to atomic size as you move down a group?

  It increases
• Order the following elements by increasing atomic size down a group:

  1️⃣ Lithium

  2️⃣ Sodium

  3️⃣ Potassium

  4️⃣ Rubidium

  5️⃣ Cesium
• The atomic number of an element is equal to the number of protons in its nucleus.

  True
• What two particles primarily determine the atomic mass of an atom?

  Protons and neutrons
• Order the following elements in terms of increasing atomic size: Lithium, Beryllium, Boron, Carbon

  1️⃣ Carbon

  2️⃣ Boron

  3️⃣ Beryllium

  4️⃣ Lithium
• The atomic mass generally increases as you move from left to right across a period.


  True
• The number of neutrons in isotopes of the same element can vary.


  True
• Why does atomic mass increase as you move down a group in the periodic table?

  More protons and neutrons