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New YorkChemistry

Atomic Concepts and the Periodic Table

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How are electrons arranged in energy levels, and what is the difference between a ground state and an excited state?

Electron configuration and energy levels: write Regents electron configurations, distinguish ground state from excited state, and explain how electrons absorb and emit specific amounts of energy as photons.
A focused Regents Chemistry answer on electron configuration the New York way (shell notation such as 2-8-1), the ground state versus excited state distinction, valence electrons, and how absorbed and emitted energy produces bright-line spectra.
9 min answer →

How do atoms become ions, and how does nuclide notation record the particles in an atom or ion?

Ions and nuclide notation: explain how positive and negative ions form by losing or gaining electrons, and interpret nuclide symbols to count protons, neutrons and electrons.
A focused Regents Chemistry answer on ion formation and nuclide notation: how losing or gaining electrons makes cations and anions, why protons and neutrons stay fixed, and how to read mass number, atomic number and charge from a nuclide symbol.
8 min answer →

Why is the atomic mass on the periodic table rarely a whole number, and how do isotopes explain it?

Isotopes and average atomic mass: define isotopes, and calculate the weighted average atomic mass of an element from the masses and natural abundances of its isotopes.
A focused Regents Chemistry answer on isotopes and weighted average atomic mass: how isotopes differ in neutrons, why the periodic-table mass is a decimal, and the step-by-step weighted-average calculation the exam asks for in Part B-2 and Part C.
9 min answer →

How do atomic radius, ionization energy and electronegativity change across a period and down a group?

Periodic trends: describe and explain the trends in atomic radius, ionization energy, electronegativity and metallic character across a period and down a group, using Table S where appropriate.
A focused Regents Chemistry answer on periodic trends: atomic radius, ionization energy, electronegativity and metallic character, why each trend runs the way it does, and how to read the numbers from Table S of the Reference Tables.
9 min answer →

What are atoms made of, and how do the three subatomic particles determine an atom's identity and charge?

Atomic structure: describe the charge, relative mass and location of protons, neutrons and electrons, and use atomic number and mass number to count the particles in an atom.
A focused Regents Chemistry answer on the proton, neutron and electron: their charge, relative mass and location, how the atomic number and mass number count them, and how the wave-mechanical model superseded the Bohr and Rutherford pictures.
9 min answer →

How is the periodic table organized, and how does an element's position tell you its properties?

The periodic table and its organization: explain periods, groups and the periodic law, and classify elements as metals, nonmetals or metalloids using position and physical properties.
A focused Regents Chemistry answer on how the periodic table is arranged: periods and groups, the periodic law, the families (alkali metals, alkaline earth metals, halogens, noble gases), and how to classify metals, nonmetals and metalloids from position and properties.
9 min answer →