When do single atoms begin to pull together when they are close enough like 2 magnets?

Could 1 atom contain a magnetic field and would it be stronger than an atom's own gravity?

I know that atoms have atomic weight and bigger atoms should have more gravity.

Are there atom that repel each other if placed stationary together?

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    $\begingroup$ It will never happen because EM dominates atomic level over gravity by a factor of about 10^36 $\endgroup$ – N.S.JOHN Jan 21 '16 at 13:00

Both gravity and electrostatic forces depend on distance ($r$) like $1/r^2$. So changing the separation between 2 atoms changes both forces equally. So whichever force is stronger initially (at any distance) will always be stronger.

To determine which is stronger consider the ratio of gravitational to electric force. $$ F_g/F_e = 4\pi \epsilon_0 G \frac{m_1 m_2}{q_1 q_2} $$ Edit: Thanks to @KennyDuran for the correction!

For 2 Hydrogen atoms $$ F_g/F_e = 8.1 \times 10^{-37} $$

To give gravity the best chance of overcoming electrostatics we want a maximum mass and a minimum charge. However subatomic particles come in quantised amounts of both. Increasing the number of protons or electrons, increases both charge and mass, so they don't help. Increasing the number of neutrons would work, although you'd need to add $1.11 \times 10^{18}$ neutrons to balance $F_g/F_e$ to one. Given that nuclei quickly become unstable with excess neutrons, this will never happen.

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    $\begingroup$ Isn't it $\frac{F_g}{F_e}=G*4πϵ_0 \frac{m_1m_2}{q_1q_2}$* because the reciprocal of the electrostatic force has $4πϵ_0$ in the numerator? $\endgroup$ – Striker Jan 30 '16 at 1:37
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    $\begingroup$ @KennyDuran Good spot! Thank you! Have updated my answer with the correct formula and numbers. $\endgroup$ – Judge Jan 30 '16 at 13:10

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