Here is one Scripture that you should keep in mind when dealing with people who claim to be atheists! Psalm 14:1:
1 The [empty-headed] fool has said in his heart, There is no God. They are corrupt, they have done abominable deeds; there is none that does good or right.
If someone SAYS there is no God, THIS is what the God of the Bible says about THEM! I have always said that there are no such thing as atheists. The Bible agrees with me! Look at Romans 1:19-20:
19 For that which is known about God is evident to them and made plain in their inner consciousness, because God [Himself] has shown it to them. 20 For ever since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through His workmanship [all His creation, the wonderful things that He has made], so that they [who fail to believe and trust in Him] are without excuse and without defense.
The One, True God Himself has revealed Himself through His creation. He says in the verses above that He Himself also made clear to their inner consciousness that He IS God! So, atheists KNOW that God is, they just don't want to know Him! Keep that in mind when you find yourself in conversation with them, and then be lead by Holy Spirit in what you say! Philippians 2:10-11 tells us this:
10 That in (at) the name of Jesus every knee should (must) bow, in heaven and on earth and under the earth, 11 And every tongue [frankly and openly] confess and acknowledge that Jesus Christ is Lord, to the glory of God the Father.
Continue to share the Word of God with those who want to hear, but realize that every seed of the Word that you sow WILL have an impact on those who hear and they will be without excuse when THAT day comes! AMEN! Even now there are people who are beginning to act on something that you shared with them a long time ago, but Holy Spirit was able to finally get through to them and the Word that you spoke in THAT season, is in due season for them right now! HALLELUJAH! Remember, your rewards are for what YOU do, not for what others do with what you share! Here is Hillsong United with "No Reason to Hide":
Shalom in Him!