Atomic Structure and Discoveries Quiz

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Questions and Answers

What is the significance of valence electrons in determining the chemical properties of an element?

Valence electrons determine the combining capacity of an atom, influencing how it interacts and bonds with other atoms.

Describe the term 'valency' and how it is typically determined using hydrogen.

Valency is the number of chemical bonds an atom can form, determined by how many hydrogen atoms it can bond with.

Explain the octet rule and its relevance to stable electronic configurations.

The octet rule states that atoms tend to have eight electrons in their valence shell for stability, resulting in a filled outer shell.

How does the electronic configuration of the first 18 elements relate to their position in the periodic table?

<p>The electronic configuration correlates with an element’s position in the periodic table, as it affects its chemical properties and reactivity.</p> Signup and view all the answers

Identify two elements from the first 18 that have a valency of zero and explain why.

<p>Noble gases like helium and neon have a valency of zero due to their completely filled valence shells.</p> Signup and view all the answers

What role do valence electrons play in forming compounds like H2O, NH3, and CH4?

<p>Valence electrons determine how many bonds an atom can form, enabling the creation of compounds like H2O, NH3, and CH4 with specific bonding patterns.</p> Signup and view all the answers

How can you predict the combining capacity of an element using its valence electrons?

<p>By counting the number of valence electrons, you can predict how many atoms of hydrogen or other univalent atoms the element can bond with.</p> Signup and view all the answers

Discuss how elements with similar valence electron configurations are grouped in the periodic table.

<p>Elements with similar valence electron configurations are grouped together because they share chemical properties and reactivities.</p> Signup and view all the answers

How many electron shells are occupied in a nitrogen atom?

<p>Two shells are occupied in a nitrogen atom.</p> Signup and view all the answers

Which element has a completely filled first shell?

<p>Helium has a completely filled first shell.</p> Signup and view all the answers

What is the electronic configuration of an element with atomic number 11?

<p>The electronic configuration of sodium (atomic number 11) is $1s^2 2s^2 2p^6 3s^1$.</p> Signup and view all the answers

What discovery did J.J. Thomson make about cathode rays?

<p>J.J. Thomson discovered that cathode rays are streams of negatively charged particles called electrons.</p> Signup and view all the answers

How did Eugen Goldstein contribute to atomic theory?

<p>Eugen Goldstein discovered anode rays, which established the existence of positively charged protons.</p> Signup and view all the answers

What does Thomson’s plum-pudding model suggest about atomic structure?

<p>Thomson’s plum-pudding model suggests that atoms are composed of a uniform positive charge with negatively charged electrons scattered throughout.</p> Signup and view all the answers

How did Dalton’s atomic theory explain the law of conservation of mass?

<p>Dalton's atomic theory explained the law of conservation of mass by positing that atoms cannot be created or destroyed in a chemical reaction.</p> Signup and view all the answers

Why is understanding electron configurations important in studying element properties and bonding?

<p>Understanding electron configurations helps determine how atoms bond and interact based on their valence electrons.</p> Signup and view all the answers

What is the significance of the octet rule in determining the valency of elements?

<p>The octet rule signifies that atoms tend to gain, lose, or share electrons to achieve a full outer shell of eight electrons, influencing their valency.</p> Signup and view all the answers

How is the valency calculated for elements with four or less valence electrons?

<p>For elements with four or fewer valence electrons, the valency is equal to the number of valence electrons.</p> Signup and view all the answers

Explain how the valency of an atom changes if it has more than four valence electrons.

<p>If an atom has more than four valence electrons, its valency is calculated as 8 minus the number of valence electrons.</p> Signup and view all the answers

What is the valency of nitrogen based on its electronic configuration?

<p>The valency of nitrogen is 3, as it has 5 valence electrons and requires 3 more to complete its octet.</p> Signup and view all the answers

Describe the electron distribution for the element sodium.

<p>Sodium has an electron distribution of 2 in the K shell and 8 in the L shell, with 1 valence electron in the M shell.</p> Signup and view all the answers

What electron configuration corresponds to the element chlorine?

<p>Chlorine has an electron configuration of 2 in the K shell, 8 in the L shell, and 7 in the M shell.</p> Signup and view all the answers

Identify the atomic number and common valency of carbon.

<p>Carbon has an atomic number of 6 and a common valency of 4.</p> Signup and view all the answers

Which element has a valency of 2 and why?

<p>Oxygen has a valency of 2 because it has 6 valence electrons and requires 2 more to achieve a complete octet.</p> Signup and view all the answers

What are the valencies of aluminum and silicon, respectively?

<p>Aluminum has a valency of 3, while silicon has a valency of 4.</p> Signup and view all the answers

How does the electron configuration of an element indicate its chemical properties?

<p>The electron configuration determines the number of valence electrons, which influences an element's bonding and reactivity.</p> Signup and view all the answers

Flashcards

Valence electrons

Electrons in the outermost shell of an atom.

Valence

Combining capacity of an atom.

Valency

Number of bonds an atom can form.

Stable electronic configuration

Full outermost electron shell.

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Octet rule

Maximum of 8 electrons in the valence shell for main group elements.

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Chemical activity

Ability of an element to combine or react with other elements.

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Combining capacity

The ability of an atom to join with other atoms to form chemical bonds.

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Univalent atom

Atom forming one bond.

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What are cathode rays?

Cathode rays are streams of negatively charged particles called electrons, emitted from the cathode in a cathode ray tube when high voltage is applied.

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What are anode rays?

Anode rays are streams of positively charged particles called protons, emitted from the anode in a discharge tube with a perforated cathode.

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What is Thomson's plum pudding model?

Thomson's model suggested that the atom is a sphere of uniform positive charge with negatively charged electrons scattered throughout, like plums in a pudding.

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How did Dalton's atomic theory change?

Dalton's theory initially considered the atom as the smallest indivisible particle, but the discovery of subatomic particles like electrons and protons showed that atoms are not indivisible.

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What's the importance of electronic configuration in bonding?

Understanding electronic configurations of atoms is crucial for studying how elements form bonds, which is explored in detail in a later lesson.

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What did Dalton's atomic theory explain?

Dalton's theory explained the law of conservation of mass, law of constant composition, and law of multiple proportions.

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What is the first shell called?

The first shell, which can hold up to two electrons, is called the K shell.

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What element has a completely filled first shell?

The element Helium (He) has a completely filled first shell with two electrons.

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How does valency relate to octet rule?

Valency is determined by how many electrons an atom needs to gain, lose, or share to achieve a stable octet.

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Predicting valency for elements with 4 or less valence electrons

Valency is equal to the number of valence electrons.

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Predicting valency for elements with more than 4 valence electrons

Valency is equal to 8 minus the number of valence electrons.

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Example: Fluorine

Fluorine has 7 valence electrons, so its valency is 1 (8 - 7 = 1).

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Example: Carbon

Carbon has 4 valence electrons, so its valency is 4.

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What does the table show?

The table demonstrates the relationship between atomic number, electron configuration, and valency for elements 1 - 18.

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What is the importance of understanding valency?

Predicting the types of bonds an element can form and the resulting chemical compounds.

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Study Notes

Atomic Structure

  • Atoms are the smallest constituents of matter
  • Dalton's atomic theory proposed atoms as indivisible
  • Modern understanding of atoms reveals subatomic particles (electrons, protons, neutrons)
  • Electrons are negatively charged
  • Protons are positively charged
  • Neutrons are neutral

Discovery of Electron

  • Sir William Crookes studied cathode rays
  • Cathode rays are streams of negatively charged particles
  • J.J. Thomson determined the charge-to-mass ratio of the electron
  • Cathode rays are streams of electrons

Discovery of Proton

  • Eugen Goldstein discovered anode rays (positive rays)
  • These rays were composed of positively charged particles (protons)
  • Protons were found to be present in all atoms

Rutherford's Model

  • α-particles scattered by gold foil
  • Most α-particles passed straight through
  • A few α-particles were deflected at large angles
  • Rutherford proposed a nuclear model with a dense, positively charged nucleus
  • Electrons orbit the nucleus

Bohr's Model

  • Electrons orbit the nucleus in specific energy levels (orbits)
  • Electrons do not radiate energy in these orbits
  • Electrons can change energy levels by absorbing or emitting photons of energy
  • Each shell has a maximum capacity of electrons (2n2)

Subatomic Particles

  • Table with characteristics of electron, proton, and neutron (mass, charge, location)

Atomic Number and Mass Number

  • Atomic number (Z) = number of protons in the nucleus
  • Mass number (A) = number of protons + number of neutrons
  • Atomic symbol notation (e.g., 126C)

Electronic Configuration

  • Distribution of electrons in different energy levels (shells)
  • Shells are labeled K, L, M, N, etc. (or n = 1, 2, 3, 4, ...)
  • Maximum number of electrons in a shell = 2n2
  • Electronic configuration notation (e.g., 2, 8, 1 for sodium)

Concept of Valency

  • Valency: Combining capacity of an element
  • Valency depends on the number of valence electrons

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