Atomic Structure
18 questions tagged Atomic Structure — spanning every one of the seven Ws.
Which element has the highest ionization energy?
Helium has the highest first ionization energy of any element, about 24.6 electron volts. It is very difficult to remove an electron from a helium atom.
Which element has the lowest ionization energy?
Francium is generally expected to have the lowest first ionization energy, but because it is extremely rare and radioactive, this is based on theory rather than extensive direct measurement. Cesium is very close and is the most commonly referenced practical example.
Which element has the largest atomic radius?
Francium is usually cited as having the largest atomic radius, though direct measurements are limited by its rarity and radioactivity. In practice, cesium is the nearest well-studied comparison.
Whose discovery made it possible to measure very large atoms and molecules by mass spectrometry?
J. J. Thomson is associated with early mass spectrograph work in 1912 and the idea of isotopes. His studies helped show that atoms of the same element can have different masses.
Whose work created the concept of isotopes?
Frederick Soddy introduced the concept of isotopes in 1913. He showed that atoms can have the same chemical identity but different masses.
How do atoms become ions?
Atoms become ions when they gain or lose electrons. Losing electrons makes a positive ion, while gaining electrons makes a negative ion.
How does the periodic table show electron shells?
The row number often matches how many electron shells an element has. As you move across a row, electrons fill the same shell in a predictable pattern.
Why are isotopes of the same element chemically similar?
Isotopes have the same number of protons and electrons, so they have nearly the same chemistry. They mainly differ in neutron number and mass.
What is an electron shell?
An electron shell is a main energy level around an atom’s nucleus where electrons are found. Shells help explain why atoms bond and how the periodic table is organized.
When was the proton first identified as a distinct particle?
Around 1917–1919, Ernest Rutherford identified the proton as the hydrogen nucleus in nuclear reactions. It became recognized as a fundamental particle of positive charge.
Whose idea introduced electron shells and explained periodic patterns?
Niels Bohr’s. In 1913 he proposed that electrons occupy quantized shells around the nucleus.
Whose experiment showed that alpha particles could reveal the atom’s tiny nucleus?
Ernest Rutherford’s. The gold foil experiment, done in 1909, showed that atoms have a small, dense nucleus.
How does an element get its atomic number?
An element’s atomic number is the number of protons in its nucleus. This number defines the element’s identity and place in the periodic table.
What are valence electrons?
Valence electrons are the outermost electrons of an atom, and they largely control how an element reacts chemically. Elements with similar valence-electron patterns often behave in similar ways.
Whose experiment first proved that atoms can be split into subatomic particles by studying alpha particles?
Ernest Rutherford’s. Between 1909 and 1911, his gold foil experiment showed that atoms have a small, dense nucleus.
How many electrons can the first shell hold?
The first electron shell can hold 2 electrons. Once it is full, the atom is especially stable.
How many electrons can the second shell hold?
The second shell can hold up to 8 electrons. That is a key reason the periodic table has repeating chemical patterns.
How many electrons can the third shell hold?
In basic chemistry, the third shell is often taught as holding 8 electrons, but in the full quantum model it can hold up to 18. That is why chemistry becomes more complex after the second period.